Systems and methods for reducing weighing errors associated with partially off-scale items

ABSTRACT

Systems and methods are provided for reducing erroneous weighing of items by detecting items extending beyond a peripheral edge of a weigh platter associated with a data reader. For example, in response to a weigh request a scale guard module acquires data indicative of whether an item extends between the weigh platter and another surface, compares the acquired data to reference data, and based on the comparison, determines whether an item extends off the weigh platter and thus on to another surface. The scale guard module may utilize non-electromagnetic compression waves, radio waves, a portion of a data reader&#39;s scan field to scan a set of patterns extending along at least one edge of the weigh platter, an imaging based scanner to capture an image of at least one edge of the weigh platter, light beams extending along at least one edge of the weigh platter, or any combination thereof.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 61/121,058, filed Dec. 9, 2008 and U.S.Provisional Application No. 61/267,376, filed Dec. 7, 2009, both ofwhich a hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The field of the present disclosure relates generally to data readersand, in particular, to reducing or otherwise mitigating weighing errorsassociated with data readers equipped with a weigh scale.

BACKGROUND INFORMATION

Data readers, such as barcode scanners and RFID readers, are a popularmeans for data acquisition in computerized processing systems. Barcodescanners are used to read and decode barcode patterns or other symbolsor information imprinted on different surfaces in order to transmit theinformation encoded in the barcode pattern or symbol to a hostprocessing device.

Certain data readers are equipped with a scale, such as a flush-mountedscale incorporated into point-of-sale checkout counters, to provide aspace efficient solution to reading barcode information associated withan item and weighing the item. If the item or object to be weighedoverhangs an edge of the scale, an inaccurate measurement may bereturned by the scale. For example, if an item to be weighed partiallyrests on the counter, the scale may return a lower weight. By way ofanother example, if one or more items on the counter partially rest onthe scale while another item is being weighed, the scale may return ahigher weight. Thus, if the overhanging condition goes unnoticed, acustomer may be overcharged or undercharged for the item.

Accordingly, the present inventors have recognized a need to detectevents resulting in inaccurate weight measurements, such as when an itemspans the scale and the checkout counter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a multiplane scanner, according to oneembodiment.

FIG. 2 is a high-level block diagram of the scanner of FIG. 1, whichincorporates a scale guard module.

FIG. 3 is a high-level block diagram of an imaging based scanner,according to one embodiment.

FIG. 4 is a high-level block diagram of a laser based scanner, accordingto one embodiment.

FIG. 5 is a perspective view of a multiplane scanner including anultrasonic scale-guard system, according to one embodiment.

FIGS. 6A and 6B are high-level block diagrams of a multiplane scannerincluding an ultrasonic scale-guard system, according to variousembodiments.

FIG. 6C is a block diagram of an example a transmitter and receiver foran ultrasonic scale-guard system.

FIG. 6D is a schematic diagram of an example transmitter for anultrasonic scale-guard system.

FIG. 6E is a schematic diagram of an example receiver for an ultrasonicscale-guard system.

FIG. 7 is a high-level flowchart illustrating a method for reducingweighing errors associated with data readers, according to oneembodiment.

FIG. 8 a high-level block diagram of a multiplane scanner including aradiofrequency scale-guard system, according to one embodiment.

FIG. 9A is a block diagram of an example radiofrequency transmitter.

FIG. 9B is a schematic diagram of an example radiofrequency transmitter.

FIG. 10A is a block diagram of an example radiofrequency receiver.

FIG. 10B is a schematic diagram of an example radiofrequency receiver.

FIG. 11 is a high-level flowchart illustrating a method for reducingweighing errors associated with data readers, according to anotherembodiment.

FIGS. 12A, 12B, 12C, and 13 are high-level block diagrams of amultiplane scanner including a light beam scale-guard system, accordingto one embodiment.

FIG. 14 is a high-level flowchart illustrating a method for reducingweighing errors associated with data readers, according to yet anotherembodiment.

FIG. 15 a perspective view of a multiplane scanner including anperimeter-pattern scale-guard system, according to one embodiment.

FIG. 16 is a high-level flowchart illustrating a method for reducingweighing errors associated with data readers, according to still anotherembodiment.

FIGS. 17 and 18 are example images captured by an imaging based scanner.

FIGS. 19 and 20 are plan views of weigh platters incorporating uniformand non-uniform perimeter patterns, respectively.

FIGS. 21 and 22 are example scan signals from scans of uniform andnon-uniform perimeter patterns, respectively.

FIG. 23 is a high-level block diagram of a multiplane scanner includingan edge-vision scale-guard system, according to one embodiment.

FIG. 24 is an example image captured by the scanner of FIG. 23.

FIG. 25 is a high-level flowchart illustrating a method for reducingweighing errors associated with data readers, according to yet anotherembodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference to the above-listed drawings, this section describesparticular embodiments and their detailed construction and operation.The embodiments described herein are set forth by way of illustrationonly. In light of the teachings herein, those skilled in the art willrecognize that there may be equivalents to what is expressly orinherently taught herein. For example, variations can be made to theembodiments described herein and other embodiments are possible. It isnot always practical to exhaustively catalog all possible embodimentsand all possible variations of the described embodiments.

For the sake of clarity and conciseness, certain aspects of componentsor steps of certain embodiments are presented without undue detail wheresuch detail would be apparent to those skilled in the art in light ofthe teachings herein and/or where such detail would obfuscate anunderstanding of more pertinent aspects of the embodiments.

Overview

Before describing detailed examples of systems and methods for reducingweighing errors associated with partially off-scale items, arepresentative data reader and associated concepts will first bedescribed.

FIG. 1 is a perspective view of a data reader or scanner system 100,according to one embodiment. The scanner system 100 comprises a datareader equipped with a weigh scale comprising a weigh platter 110 forweighing retail items, such as produce or bulk items, at thepoint-of-sale. The weigh platter 110 may be rectangular as shown in FIG.1, or may comprise another geometric shape, such as a polygon or curvedshape. The scanner system 100 includes a housing 120 with a lowerhousing portion 122 and an upper housing portion 124. A data reader oroptical code reader, such as imaging based scanner 180 (FIG. 2), laserbased scanner 190, or both, obtains data for reading encoded symbolsthrough a lower window 130 supported on the lower housing 122 and anupper window 132 supported on the upper housing 124. The lower window130 is arranged in a generally horizontal plane and the upper window 132is arranged in a generally vertical plane.

The system 100 may include input devices, such as one or more buttons140 typically disposed on the housing 120, that allow a user to interactwith the scanner system 100 (e.g., for zeroing the scale or adjusting avolume of a beep tone indicating that a bar code on an item has beensuccessfully read by the scanner or a sound indicating an off-scalecondition). The housing 120 may also include external indicia orindicators, such as scanner and scale status lights (e.g.,light-emitting diodes (LEDs)) 150 or an alert 152, to notify the user ofvarious scanner states.

The weigh platter 110 may include an integrated two-plane weigh platter(or other single-plane or multi-plane weigh platter) that allows itemsto be placed on a substantially horizontal portion of weigh platter 110,a substantially vertical portion of weigh platter 110, or both, to beweighed. One such two-plane weigh system is the All-Weighs® plattersystem available from Datalogic Scanning, Inc. of Eugene, Oreg., furtherdescribed in U.S. Pat. No. RE40,071, which is hereby incorporated byreference in its entirety. A fruit rail or shoulder 112 extending abovethe horizontal surface and disposed at the checker-side edge of theweigh platter 110 may be provided to help rest bulky items against thevertical portion of weigh platter 110. Preferably, the scanner system100 is supported by a checkout counter 160 so that the weigh platter 110is substantially flush with the checkout counter 160. While the counter160 may extend along two opposing or edges of the weigh platter 110, thecounter may only extend along all or a portion of one edge of the weighplatter 110 or the counter may also extend along a foot or fruit railedge of the weigh platter 110 or upper housing edge of the weigh platter110. According to one embodiment, the weigh platter 110 may be separatedby a gap from the counter 160 or other fixed object, such as a scannerframe or lower housing portion 122.

For purposes of description, certain sides of the weigh platter will nowbe defined, in this case with respect to FIG. 1 but the terminology isapplicable to each of the embodiments. A top surface of the weighplatter 110 may be described as having a generally rectangular shapethus having four sides or edges defined as follows: (1) a proximal sideedge is the edge nearest the upper housing portion 124, the proximalside may also be described as the customer side; (2) a distal side edgeis the furthest from the upper housing portion 124 and thus next to thefruit or foot rail 112, the distal side may also be described as thechecker side because it is the side normally nearest the checker in acommon installation; (3) a first or left lateral side edge 114; and thesecond or right lateral side edge 116 is the lateral side. The left andright opposing lateral side edges 114 and 116 may be adjacent respectiveedges of a top surface of the checkout counter 160 or other fixedobject, such as a scanner frame or lower housing portion 122.

FIG. 2 is a block diagram showing operational components of the scannersystem 100, according to one embodiment. While a bus-based architecture,based on a bus 170, is illustrated in FIG. 2, other suitable types ofarchitectures may be employed, such as one or more of the componentsdirectly coupled or connected to each other. The scanner system 100incorporates two types of optical code readers, namely imaging basedscanners 180 a and 180 b and laser based scanners 190 a and 190 b. Theimaging based scanner 180 a and laser based scanner 190 a attempt toread encoded symbols through the upper window 132 while the imagingbased scanner 180 b and laser based scanner 190 b attempt to readencoded symbols through the lower window 130. Other positions orconfigurations of the scanners may be employed. For example, the scannersystem 100 may include only imaging based scanners 180 a and 180 b, onlylaser based scanners 190 a and 190 b, or any combination thereof.

Imaging based scanners 180 a and 180 b include solid state imagecircuitry, such as charge coupled devices (CCDs) or CMOS imagers, andmay be implemented using a one-dimensional or two-dimensional imagingarray of photosensors to capture a barcode. One-dimensional CCD readerscapture a linear cross section of the barcode at once, producing ananalog waveform whose amplitude represents the relative darkness andlightness of the barcode. Two-dimensional CCD readers capture an entiretwo-dimensional image at once.

Laser based scanners 190 a and 190 b may comprise a flying spot laserbarcode scanner that obtains barcode information by sweeping a laserspot across a barcode. The laser spot may be generated by a laser lightsource which is then directed towards an oscillating reflecting surface,typically a mirror. The light reflected from the barcode is collected bya photosensor, which outputs an analog waveform representing therelative spacing of the bars in the barcode. The analog signal may thenbe digitized and decoded into data representing the information encodedin the barcode.

The scanner system 100 may include any combination of componentssuitable for scanning optical codes, such as bar codes, industrialsymbols, alphanumeric characters, or another machine-readablerepresentation of information in a visual format on a surface of theobject. In addition, the scanner system 100 may include other types ofdata readers, such as a radiofrequency identification (RFID) reader. AnRFID system typically employs a transponder or tag, which is attached tothe physical item to be identified, and a reader, which sends anelectromagnetic signal to the transponder and then detects a response.Typically, the reader emits an RF signal which is received by thetransponder after the transponder comes within an appropriate range. Inresponse to the signal from the reader, the transponder sends amodulated RF signal back to the reader. The reader detects thismodulated signal and can identify the transponder by decoding themodulated signal. After identifying the transponder, the reader caneither store the decoded information or transmit the decoded signal to acomputer.

A scale module or weigh scale 200 is provided to determine the weight ofan item placed on the weigh platter or platform 110 (e.g., resting onthe horizontal portion, vertical portion, or both). According to oneembodiment, the scale module 200 includes components to measure thegravitational force acting on the item. For example, one or more loadcells may be interposed between the weigh platter 110 and a frame orother rigid support of the scanner system 100. When an item is placed onthe weigh platter 110, the weight of the item deflects the load cell,which generates an analog or digital signal indicative of the weight ofthe item. A rigid frame or spider may be interposed between the weighplatter 110 and the load cell to provide additional support for theweigh platter 110. However, the scale module 200 may be spiderless ifthe weigh platter 110 is sufficiently rigid itself. The load cell maycomprise a machined piece of aluminum (or other material) having one ormore strain gauges attached thereto. Thus, when a mechanical stress isapplied to the load cell, the strain gauges generate signals indicativeof the stress. In place of or in addition to the strain gauges,deflection of beam supporting the item may be measured optically.

A scale guard module 210 is provided to determine whether an item restsor partially rests on a surface other than the weigh platter 110, suchas the counter 160 or other fixed object, such as a scanner frame orlower housing portion 122 (e.g., the item extends between the weighplatter 110 and the counter 160), which may affect the accuracy of theweight measurement. According to one embodiment, the scale guard module210 is used in association with a weigh platter that is installed in aretail checkout counter or other fixed object (e.g., a supermarketcheckout counter). According to another embodiment, the scale guardmodule 210 is used in association with a weigh platter that is installedin another checkout counter or other fixed object, such as a checkoutcounter or other fixed object used in connection with mail, parcel, orluggage sorting.

The scale guard module 210 may, for example, be configured to, inresponse to a weigh request (e.g., from host 292), acquire dataindicative of whether an item extends between the weigh platter andanother surface, compare the acquired data to reference data, and basedon the comparison, determine whether an item extends between the weighplatter and another surface (e.g., rests partially on the checkoutcounter or other fixed object and partially on the weigh platter 110).The scale guard module 210 may utilize non-electromagnetic compressionwaves, radio waves, a portion of a data reader's scan field to scan aset of patterns extending along at least one edge of the weigh platter,an imaging based scanner to capture an image at least one edge of theweigh platter, a light beam extending along at least one edge of theweigh platter, or any combination thereof, to determine whether an itemextends between the weigh platter and another surface. The scale guardmodule 210 may comprise hardware, software, firmware, or any combinationthereof, and may comprise a set of instructions stored in a memory, suchas memories 250 and 260. Various embodiments of the scale guard module210 will be described in more detail with respect to FIGS. 5-25.

According to one embodiment, a system for reducing weighing errorsassociated with data readers equipped with a weigh platter comprises ascale module for determining the weight of an item placed on the weighplatter and a non-light-beam-based scale guard module configured to, inresponse to a weigh request received from a host and withouttransmitting a light beam along an edge of the weigh platter at apredetermined distance above a surface of the weigh platter, acquiredata indicative of whether an item extends between the weigh platter andanother surface, compare the acquired data to reference data, and basedon the comparison of the acquired data to the reference data, determinewhether an item extends between the weigh platter and another surface.

The non-light-beam-based scale guard module may, according to oneembodiment, utilize non-electromagnetic compression waves to determinewhether an item extends between the weigh platter and another surface.According to another embodiment, the non-light-beam-based scale guardmodule may comprise an array of emitters extending along opposing edgesof the weigh platter and configured to transmit non-electromagneticcompression waves, a sensor configured to detect incident compressionwaves from the emitters, and a controller communicatively coupled to thesensor, the controller configured to determine whether an item extendsbetween the weigh platter and another surface by monitoring the sensorfor an alteration of one or more compression waves transmitted by theemitters. According to still another embodiment, thenon-light-beam-based scale guard module utilizes radio waves todetermine whether an item extends between the weigh platter and anothersurface. According to still a further embodiment, thenon-light-beam-based scale guard module comprises the weigh platterconfigured to form a radiating antenna for transmitting electromagneticwaves across at least one edge of the weigh platter, a set of receivingantennas configured to receive the electromagnetic waves from the weighplatter, and a RF receiver coupled to the set of receiving antennas andconfigured to monitor the set of receiving antennas for alterations inthe electromagnetic waves indicative of whether an item extends betweenthe weigh platter and another surface.

According to yet another embodiment, the non-light-beam-based scaleguard module utilizes a portion of a scan field of the data reader toscan a set of patterns extending along opposing edges of the weighplatter to determine whether an item extends between the weigh platterand another surface. According to still another embodiment, thenon-light-beam-based scale guard module comprises a pattern extendingalong opposing edges of the weigh platter, an optical code reader, suchas an imaging based scanner or a laser based scanner, configured todetect at least a portion of the pattern on each edge of the weighplatter, and a controller communicatively coupled to the optical codereader and configured to determine whether an item extends between theweigh platter and another surface based on whether the item interruptseither of the patterns extending along opposing edges of the weighplatter. According to yet another embodiment, the non-light-beam-basedscale guard module utilizes an imaging based scanner to capture an imageof opposing edges of the weigh platter to determine whether an itemextends between the weigh platter and another surface. According tostill another embodiment, the non-light-beam-based scale guard modulecomprises an imager for capturing an image of at least a portion of theweigh platter and a processor communicatively coupled to the imager, theprocessor configured to determine whether an item extends between theweigh platter and another surface by comparing the captured image of theweigh platter with a reference image.

Other examples of systems and methods for reducing weighing errorsassociated with data readers equipped with a weigh platter are describedin U.S. Provisional Application No. 61/267,376, filed Dec. 7, 2009. Forexample, the scale guard module 210 may comprise a light source disposedin or on a housing of a scanner for producing a light beam along an edgeof the weigh platter, a detector for receiving the light beam, thedetector disposed in or on the housing, and a light guide or pipedisposed in the weigh platter for routing the light beam to thedetector, wherein the detector is operative for detecting aninterruption of the light beam due to an item overhanging an edge of theweigh platter. By way of another example the scale guard module 210 maycomprise one or more light sources, which are highly divergent, pointedupward at an angle towards a gap between the weigh platter peripheraledge and a scanner housing frame (or the checkout counter if thescanner-scale does not include such a frame), the light producing fanshaped beams which are partially obstructed by the perimeter frame andweigh platter. The portion of light beams which do not strike anyobjects crossing the gap essentially form planes of light exiting theair gap in the substantially vertical direction, this plane of light maybe referred to as a light curtain. When an object placed on the weighplatter such that a portion of it extends across the air gap, some ofthe light rays propagating up and out of the gap strike the objectscattering light rays, some of which are sensed by the detector with thesystem then alerting the operator of the off scale item.

An alert module 220 may be provided to notify the user that an item maynot be accurately weighed (e.g., the item extends between the weighplatter 110 and the counter 160). For example, the alert module 220 mayactivate a visual indication or light source, such as an alert light orLED 152, to notify the user whether or not the item extends between theweigh platter 110 and the counter 160. The alert 152 may emit light toindicate an acceptable condition, a perimeter violation, or both (e.g.,via different colors). The alert 152 may be mounted in variouslocations, such as on the upper housing portion 124, the lower housingportion 122, or within the housing 120 so that the visual indication isvisible through air gaps between the weigh platter 110 and the counter160. By way of another example, the alert module 220 may activate anaudible indication (via a speaker 222) of whether or not the itemextends between the weigh platter 110 and the counter 160. According toa one embodiment, the alert module 220 is configured to indicate whichedge of the weigh platter the item spans so that the user knows where tolook for the overhanging item. For example, there may be an alert 152for each edge of the weigh platter 110.

An interlock module 230 may be provided to disable the weighing function(or the reporting thereof) if an item is detected by the scale guardmodule 210 as extending between the weigh platter 110 and the counter160 or other fixed object. The interlock module 230 may be configured todisable the weighing function until the item is detected as no longerextending between the weigh platter 110 and the counter 160 or otherfixed object. The interlock module 230 may be implemented in hardware,software, firmware, or any combination thereof. The scanner system 100may also include an override module, such as a switch or button, toallow a transaction to proceed even if an item extends between the weighplatter 110 and the counter 160 (e.g., if the scale guard module is notfunctioning properly).

The scanner system 100 may include a number of other components thatinterface with one another via the bus 170, including a processor 240,memories 250 and 260, a display controller and display device 270, aninput controller 280, and a network interface 290. The processor 240 maybe any commercially available processor or other logic machine capableof executing instructions. Additionally, more than one processor may beprovided. The display controller and display device 270 may be providedto present data, menus, and prompts, and otherwise communicate with theuser via one or more display devices, such as a transmissive orreflective liquid crystal display (LCD), cathode ray tube (CRT) display,or other suitable display.

The standard input controller 280 may be provided to receive user inputfrom a keyboard, a pointing device, or other wired/wireless inputdevices. Other input devices may be included, such as a microphone,touchscreen, touchpad, and trackball. While the input devices may beintegrated into the scanner system 100 and coupled to the processor 240via the input controller 280, input devices may also connect via otherinterfaces, such as a connector 282. The connector 282 may include oneor more data interfaces, bus interfaces, wired or wireless networkadapters, or modems for transmitting and receiving data. Accordingly,the input controller 280 may include one or more of hardware, software,and firmware to implement one or more protocols, such as stackedprotocols along with corresponding layers. Thus, the connector 282 mayfunction as one or more of a serial port (e.g., RS232), a UniversalSerial Bus (USB) port, and an IR interface. The input controller 280 mayalso support various wired, wireless, optical, and other communicationstandards.

The network interface 290 may be provided to communicate with one ormore hosts 292 or other devices. For example, data gathered by, ordecoded by, the image based scanners 180 or laser based scanners 190 maybe passed along to the host computer 292. The network interface 290 mayfacilitate wired or wireless communication with other devices over ashort distance (e.g., Bluetooth™) or nearly unlimited distances (e.g.,the Internet). In the case of a wired connection, a data bus may beprovided using any protocol, such as IEEE 802.3 (Ethernet), AdvancedTechnology Attachment (ATA), Personal Computer Memory Card InternationalAssociation (PCMCIA), and USB. A wireless connection may use low or highpowered electromagnetic waves to transmit data using any wirelessprotocol, such as Bluetooth™, IEEE 802.11b (or other WiFi standards),Infrared Data Association (IrDa), and radiofrequency identification(RFID).

The scanner system 100 may include memory 250, which may be implementedusing one or more standard memory devices. The memory devices mayinclude, for instance, RAM 251, ROM 252, and EEPROM devices, and mayalso include magnetic or optical storage devices, such as hard diskdrives, flash memory, CD-ROM drives, and DVD-ROM drives. The scannersystem 100 may also include an interface 262 coupled to an internal harddisk drive 260. In addition, the interface 262 may also be coupled to amagnetic floppy disk drive (not shown), an optical disk drive (notshown), or another drive and may be configured for external driveimplementations, such as over a USB, IEEE 1194, or PCMCIA connection.

According to one embodiment, any number of program modules are stored inthe drives (e.g., drive 260) and ROM 252, including an operating system(OS) 253, one or more application programs 254, other program modules255 (e.g., instructions to implement the methods for reducing weighingerrors of an item being weighed), and data 256. All or portions of theprogram modules may also be cached in RAM 251. Any suitable operatingsystem 253 may be employed.

Other versions of the scanner system 100 may have less than all of thesecomponents and/or may contain other components. In a preferredconfiguration, the scanner system 100 comprises a fixed scanner, such asa Magellan® scanner manufactured by Datalogic Scanning, Inc. of Eugene,Oreg. However, the scanner system 100 may also comprise a portablescanner coupled to a scale or other device for weighing an object.

FIG. 3 is diagram of an imaging based scanner 180 for forming an imageof an item or object 300, according to one embodiment. The object 300may be any object, but in one preferred use, the object 300 is an itemupon which is printed an optical code, such as a bar code. The imagingbased scanner 180 comprises an illumination source 310, a lens assembly320, an imager 330, and a signal processor 340. The imaging basedscanner 180 may comprise other components not illustrated or may omitcertain components illustrated, such as the illumination source 310. Theillumination source 310 may comprise any source of light, such as a rowof light emitting diodes (LEDs), flash strobes, or incandescent orfluorescent lamps.

The lens assembly 320 may comprise any number of lenses for focusinglight on imager 330. For example, lens assembly 320 may comprise asingle optical element or may comprise an array of optical elements witha common axis. The lens assembly 320 may also comprise a zoom lenscoupled to the processor 240 to control an amount of optical zoom. Theimager 330 forms an electronic image of the object 300. The imager 330may comprise a wide range of image sensing devices for converting anoptical image (or another wave in the electromagnetic spectrum) into anelectrical signal. For example, the imager 330 may be a digital camera,such as a charge-coupled device (CCD) camera or complimentarymetal-oxide semiconductor (CMOS) camera, both of which form aone-dimensional or two-dimensional array of pixels, which togetherconstitute an electronic representation of the image. Each pixellocation stores data indicative of the light intensity at that locationof the image. The light intensity data for each pixel may be acolor-coded vector (e.g., red-green-blue) or monochrome intensity (e.g.,grayscale).

After the imager 330 has been exposed to light reflected by the object300, data from all the pixels can be sequentially read out in aselectable pattern (which may be row-by-row, column-by-column, or someother pattern). The signal processor 340 conditions the data receivedfrom the imager 330 and may generate an output that generally identifieswhich regions of the image correspond to light areas, and whichcorrespond to dark areas. For example, the signal processor 340 may setthe exposure time and thresholding so that the bars or relatively darkerregions of the barcode or other target are reported as being dark, andthe spaces or relatively lighter regions between the bars or darkerregions are reported as being light, according to any of a number oftechniques. Either analog or digital signal processing may be utilizedin the signal processor 340, which may include, for example, a virtualscan line extraction module, an edge detection module, and one or moredecoders (e.g., low level decoders and high level decoders). The virtualscan line extraction module may read or assemble samples or pixels fromthe imager 330 lying along one or more lines across the image atarbitrary angles or in another desired scan pattern. The resultingordered set of pixels is sometimes referred to as a “virtual scan line”because it is analogous to a signal generated by reflection of a movinglaser beam spot as it scans across the object.

The edge detection module identifies edge transition locations using anynumber of edge detection techniques. Because edges in images generallyhave strong intensity contrasts, an increase (or decrease) in intensityfrom one pixel to the next is indicative of an edge. Accordingly, manyedge detection techniques involve calculating a derivative of theintensity changes in pixel values (e.g., intensity changes between afirst pixel and an adjacent pixel or more than one adjacent pixel). Withregard to a first derivative, an edge transition can occur at a localmaxima. With regard to second derivatives, edges occur at zerocrossings. The edge detection process disclosed in U.S. PatentPublication No. 2008/0169347, which is hereby incorporated by referencein its entirety, discloses attempting to locate edges by convolvingimage data with a kernel that approximates a first or second derivative.Additionally, any number of other edge detection techniques may be used,such as subpixel edge detection. Subpixel edge detection may reduce thenumber of pixels needed for a given image region by interpolatingsubpixels between integer pixels. Further details of subpixel edgedetection can be found in U.S. Pat. No. 5,446,271, which is herebyincorporated by reference in its entirety.

Based on the edge locations, a low level decoder, a high level decoder,or both, may convert the sequence of edges and spacing between the edgesinto data usable by the host 292. For example, the low level decoder mayconvert the sequence of edges and spacing between the edges into a setof barcode elements, such as bars and spaces, and the high level decodermay convert the barcode elements into characters, which may bealphanumeric. The signal processor 340 may include control logic todetermine whether decoded data should be sent to the host 292 and, ifso, when to send the decoded data to the host 292. In addition, thesignal processor 340 may further process the output from the low leveldecoder, the high level decoder, or both, before sending the data to thehost 292. For example, the decoded data (e.g., partial sections of abarcode) may be stitched together to form data representing a completebarcode. Additionally, the signal processor 260 may further compriseother modules, such as an amplification module to amplify one or morespatial frequencies, a filtering module, and a timer module. The timermodule may be used to indicate when to stop attempting to findcharacters so that the edge detection and decoder modules are preventedfrom spending too much time trying to decode data that is not readableor decodable (or at least not easily readable or decodable) or that hasalready been decoded. While the imager 330 and the signal processor 340may be contained in the same integrated circuit, the signal processor340 may be implemented by the processor 240 (FIG. 2).

FIG. 4 is a diagram of a laser based scanner 190, according to oneembodiment. The laser based scanner 190 includes a front end 400, aphotodetector 410, and a signal processor 420. The front end 400includes a controller 430, a light source 440, a spinner 450, and one ormore pattern mirrors 460. The controller 430 is the primary interfacebetween the scanner system 100 and the components of the front end 400.Thus, the controller 430, among other things, determines whether thelight beam generated by the light source 440 is on or off and may alsocontrol the brightness of the light beam.

The light source 440 projects a scanning beam out to the object 300(e.g., that may contain a barcode or other symbol). Preferably, thelight source 440 comprises a laser diode. Alternatively, other types oflight sources, such as a He—Ne laser, other types of lasers, and/orfocused beams of non-laser light may be used instead of a laser diode.

Scanning with the light beam is accomplished using a beam oscillator450. The beam oscillator 450 may comprise an oscillating mirror drivenby an oscillating beam dither driver. Movement of the oscillating mirrorcauses the scanning light beam to move back and forth, and to therebytrace a line-shaped path over the target barcodes or other targetsymbols or indicia. However, the beam oscillator 450 may take otherforms. For example, the beam oscillator 450 may comprise a rotatingpolygon with a plurality of mirrored facets.

One or more pattern mirrors 460 may be aligned around the circumferenceof the beam oscillator 450 for deflecting a set of scan beams outwardlythrough the lower window 130 or upper window 132. Thus, the patternmirrors 460 generate respective scan lines 462 across the object 300 ina collective scan pattern, such as scan pattern 464. As the beamoscillator 450 oscillates (or rotates) through its scan arc, theresultant light beam traverses corresponding ones of the pattern mirrors460, which in turn create corresponding scan lines 462. For example, ifthe beam oscillator 450 comprises a rotating polygon having fourmirrored facets, each facet reflects an incident light beam (e.g., fromthe laser 440) outwardly along a respective 180° scanned arc as thepolygon rotates.

As the scanning beam from the light source 440 sweeps across the object300 (e.g., with a barcode or other symbol), the scanning beam isreflected by the object 300. Because the bars of the barcode have lowerreflectivity than the spaces between the bars, the amount (or intensity)of reflected light will vary depending on whether the projected spot ofthe scanning beam is incident upon a bar or a space.

The light reflected from the object 300 is collected by appropriatecollection optics (which may include lenses and/or collecting mirrors),and directed towards a photodetector 410, such as a photodiode. Thereflected beam follows a return path that is generally similar to theforward path (e.g., the reflected beam reflects off of a respectivepattern mirror 460 toward the beam oscillator 450), but diverges awayfrom the forward scan path to avoid obstruction of the forward path. Thephotodetector 410 converts variations in incident light level into asignal that has features (i.e., peaks and valleys) which correspond (inwidth) to the physical width of relatively darker and relatively lighterportions of the surface of the object 300, which may include a symbol,indicia, or bar code to be read.

The signal output from the photodetector 410 is then processed by thesignal processor 420, which may include an amplifier 470, an edgedetector 480, and a noise reduction module 490. The amplifier 470amplifies the signal output from the photodetector 410. Preferably, thegain of the amplifier 470 is adjusted using an automatic gain control(AGC) system, in which an output of either the amplifier itself oranother component (e.g., the noise reduction circuit 490) is fed back tocontrol the gain of the amplifier 470.

The edge detector 480 locates the edges of the amplified signal outputfrom the amplifier 470 using any of a variety of techniques. Becauseedges in images generally have identifiable intensity contrasts, a jumpin intensity from one point on the signal to another point on the signalcan indicate an edge. Accordingly, the edge detector 480 may calculate aderivative of the signal to identify edges. With regard to a firstderivative, an edge transition can occur at a local maxima. With regardto second derivatives, edges occur at zero crossings. Suitabletechniques of edge detection are described, for example, in U.S. Pat.No. 5,463,211 (Arends et al.) or U.S. Pat. No. 4,000,397 (Hebert etal.), both of which are hereby incorporated by reference as if set forthfully herein. The noise reduction circuit 490 eliminates or reducesedges in the amplified signal attributed to noise, and operates forexample, by discarding or ignoring edges detected whenever the firstderivative of the amplified signal is below a threshold value.

The resulting output from the signal processor 420 indicates edgetransitions (i.e., a low-to-high or high-to-low transition)corresponding to each edge (i.e., a dark-to-light or light-to-darktransition) of the surface of the object 300, which may contain abarcode, for example. The output format largely depends on the signalprocessor configuration and may comprise a digital signal, which may beformatted in a run-length encoded or other format. The output signal isprovided to the processor 240 (FIG. 2).

The description of FIGS. 1 through 4 have provided an overview of anexample data reader and associated concepts. In light of the teachingsherein, skilled persons will be aware of equivalent architectures,implementations, and variations for data readers. The description ofFIGS. 5-25 will provide various examples of systems and methods forreducing weighing errors associated with partially off-scale items.

Ultrasonic Scale Guard

One possible implementation of the scale guard module 210 (FIG. 2)utilizes sound to determine whether an item rests or partially rests ona surface other than the weigh platter 110, such as the counter 160 or ascanner frame 610 (FIGS. 6A and 6B). According to the embodimentsillustrated in FIGS. 5 and 6A, the scale guard module 210 comprises anarray of emitters or transducers 500 extending along at least one of theopposing lateral edges of the weigh platter 110 for generatingnon-electromagnetic compression waves 520 and one or more sensors ortransducers 510 configured to detect incident compression waves 520. Ifan item being weighed rests partially on the counter 160 or scannerframe 610 and partially on the weigh platter 110 (e.g., if a carrot 530extends beyond a peripheral edge of the weigh platter 110) thecompression wave(s) 520 incident the sensor(s) 510 will be altered (aswill be described in more detail below).

The scanner system 100 a illustrated in FIGS. 5, 6A, and 6B is similarto the system 100 illustrated and described with reference to FIGS. 1-4,except the scanner system 100 a includes a scale guard module thatutilizes sound to determine whether an item being weighed rests orpartially rests on a surface other than the weigh platter 110. Thus, thescanner system 100 a may include any of the components illustrated anddescribed with reference to FIGS. 1-4, such as the scale module 200, theinterlock module 230, the alert module 220, and the data reader.

The emitter(s) 500 may be installed on the weigh platter 110 (as shownin FIG. 5), the frame or lower housing portion 610 of the scanner system100 a (as shown in FIG. 6A), the counter 160, or a combination thereof.The emitter(s) 500 may extend through the surface of the weigh platter110, the counter 160, or a frame or lower housing portion 610 of thescanner system 100 a or may be installed beneath the surface of theweigh platter 110, the counter 160, or a frame or lower housing portion610 of the scanner system 100 a. Additionally, the emitter(s) 500 may beinstalled proximate a fruit rail edge of the weigh platter 110, anupper-housing edge of the weigh platter 110, or both. Although FIGS. 5and 6A illustrate the emitter(s) 500 extending along both opposinglateral edges of the weigh platter 110, according to one embodiment theemitter(s) 500 are only included along one of the lateral edges of theweigh platter 110. If the weigh platter 110 comprises another geometricshape, such as a polygon or a circle, the emitter(s) 500 may beinstalled one or more of the edges of the polygon or around all or aportion of a perimeter of the circle.

According to one embodiment, the emitter(s) 500 comprise a plurality ofindividual linearly-aligned emitters (which may be spaced apart from oneanother). However, the emitter(s) 500 may comprise one or moreindividual emitters, which may be combined into a single component forinstallation on opposing lateral edges of the weigh platter 110.Additionally, one or more rows of emitters may be provided on eachopposing edge of the weigh platter 110. For example, with reference toFIG. 6A, one or more rows of emitters on any side of the emitter(s) 500may extend along opposing sides of the weigh platter 110.

According to a preferred embodiment, the emitter(s) 500 compriseultrasonic emitter(s) for generating a frequency greater than an upperlimit of human hearing (e.g., above approximately twenty kilohertz).However, the emitter(s) 500 may generate other non-electromagneticcompression waves, such as infrasound waves (e.g., below approximatelytwenty hertz), acoustic or sound waves within an audible range of humans(e.g., between approximately twenty hertz and twenty kilohertz), orother vibrations transmitted through a solid, liquid, or gas. While theemitter(s) 500 may comprise a piezoelectric film or crystal material,the emitter(s) 500 may comprise other materials, such as ceramics orpolymers that create compression waves upon the application of atime-varying electrical signal, such as a high-frequency signal.Additionally, the emitter(s) 500 may comprise ferromagnetic materialthat changes shape when subjected to a varying magnetic field or a setof spaced apart plates that are attracted to one another upon theapplication of a potential across the plates.

The sensor(s) 510 generate an electric potential in response to anapplied mechanical stress. Thus, the sensor(s) 510 may comprise any ofthe materials described with reference to the emitter(s) 500. While onesensor 510 may be installed in the upper housing portion 124, thescanner system 100 a may be provided with more than one sensor 510 andthe sensor(s) 510 may be installed elsewhere, such as in or on the fruitrail 112, the lower housing portion 122, or the counter 160. Forexample, the emitter(s) 500, the sensor(s) 510, or a combinationthereof, may comprise one or more transducers that both generate anddetect non-electromagnetic compression waves. If the one or moretransducers detect a compression wave reflected by the item, such as thecarrot 530, the operator can be notified that the item rests orpartially rests on the counter 160.

FIG. 6B illustrates a scanner system 100 b according to anotherembodiment in which the position of the emitter(s) 500 and sensor(s) 510are reversed. In other words, one or more emitters 500 for generatingnon-electromagnetic compression waves 520 are supported on the upperhousing 124 and an array of sensor(s) 510 extend along at least one ofthe opposing lateral edges of the weigh platter 110 to detect incidentcompression waves 520. If an item being weighed, such as a carrot 530,rests partially on the counter 160 and partially on the weigh platter110, the compression wave(s) 520 incident at the sensor(s) 510 will bealtered. While one emitter 500 may be installed in the upper housingportion 124, the scanner system 100 b may be provided with more than oneemitter 500 and the emitter(s) 500 may be installed elsewhere, such asthe fruit rail 112, the lower housing portion 122, or the counter 160.For example, the emitter(s) 500, the sensor(s) 510, or a combinationthereof, may comprise one or more transducers that both generate anddetect non-electromagnetic compression waves. If the one or moretransducers detect a compression wave reflected by the item, such as thecarrot 530, the operator can be notified that the item rests orpartially rests on the counter 160.

The sensor(s) 510 may be installed on the weigh platter 110, the counter160, a frame or lower housing portion 610 of the scanner system 100 b(as shown in FIG. 6B), or a combination thereof. The sensor(s) 510 mayextend through the surface of the weigh platter 110, the counter 160, ora frame or lower housing portion 610 of the scanner system 100 b or maybe installed beneath the surface of the weigh platter 110, the counter160, or a frame or lower housing portion 610 of the scanner system 100b. Additionally, the sensor(s) 510 may be installed proximate afruit-rail edge of the weigh platter 110, an upper-housing edge of theweigh platter 110, or both. Although FIG. 6B illustrates the sensor(s)510 extending along both opposing lateral edges of the weigh platter110, according to one embodiment the sensor(s) 510 are only includedalong one of the lateral edges of the weigh platter 110. If the weighplatter 110 comprises another geometric shape, such as a polygon or acircle, the sensor(s) 510 may be installed one or more of the edges ofthe polygon or around all or a portion of a perimeter of the circle.

Referring now to FIGS. 6A and 6B, the systems 100 a and 100 b preferablyinclude a controller 540 communicatively coupled to the emitter(s) 500,the sensor(s) 510, or a combination thereof, and configured to determinewhether an item alters the non-electromagnetic compression wave(s) 520generated by the one or more emitters 500. For example, if the sensor(s)510 are installed in the upper housing portion 124, the controller 540monitors the sensor(s) 510 to determine whether the item blocks orinterferes with the compression wave(s) 520 generated by the emitter(s)500. By way of another example, if a set of transducers are disposedalong at least one of the opposing lateral edges of the weigh platter110, the controller 540 may cause the transducers to emit compressionwaves and monitor the transducers to determine whether the item reflectsthe compression waves back toward the transducers.

The controller 540 may generate a voltage for creating a potentialdifference across surfaces of the emitter(s) 500, such as surfaces of apiezoelectric film or crystal. The voltage may comprise an impulse ormay comprise a waveform, such as a sinusoid having a predeterminedfrequency. Additionally, the controller 540 may also be coupled to atransmitter that drives the emitter(s) with a signal so that emitter(s)transmit compression waves 520 and a receiver configured to monitor thesensor(s) for an alteration in amplitude of incident compression waves.Additionally, if the emitter(s) 500 comprise a series of linearlyarranged emitters, the controller 540 may control the pulsing of eachindividual emitter or set of emitters. For example, the controller 540may be configured to generate a linear, sequential firing pattern, firesets of emitters simultaneously, or phase the firing of emitters tocreate a phased array for electronically steering an ultrasound beam.The controller 540 may be incorporated into the processor 240 (FIG. 2),or may comprise a standalone component, such as a commercially availableprocessor or other logic machine capable of executing instructions.

FIG. 6C is a block diagram illustrating an example transmitter 620 andan example receiver 660 for detecting whether an item being weighed on aweigh platter is off the weigh platter of a weight scale, which mayintroduce weighing errors. The transmitter 620 comprises a power source622 and an oscillator or driver circuit 624. The transmitter 620 iscoupled to a set of one or more emitter transducers 630 that emitultrasound compression waves 650, which are detected by a set of one ormore receiving or sensing transducers 640. The transducers 640 arecoupled to the receiver 660, which includes an amplifier 662 to amplifythe signal generated at transducers 640 by the incident compressionwaves 650. The receiver 660 may be coupled to an analog to digitalconvertor, which may be implemented in or by the controller 540 oranother circuit, to process the received signals. The piezoelectrictransducers 630, 640, or both, may be placed around one or more edges ofthe weigh platter 110 so that an object blocking one or moretransducers, such as produce hanging over an edge of the platter,reduces an output of the receiver 660, which indicates that somecorrective action needs to be taken to help prevent weighing errors. Forexample, an emitter transducer 630, such as a piezo film having adiameter of approximately one inch, may be supported on the upperhousing 124 and one or more receiving transducers 640 (each of which maycomprise, for example, a piezo film having a diameter of approximatelyone inch) may be positioned along one or more edges of the weigh platter110. According to one embodiment, the emitter transducers 630 andreceiving transducers 640 may be configured to transmit and receivenon-electromagnetic compression waves within the range of approximately200 kilohertz to approximately 400 kilohertz.

FIG. 6D is a schematic diagram of an example transmitter 620. The powersource 622 (e.g., 15 volts) and power source 623 (e.g., −15 volts)supply the necessary power to drive the emitter transducer 630. Anoscillator is formed from transistor 670, diode 671, inductor 672,capacitors 673-675, resistor 676, and resistor 677. For example, ifinductor 672 comprises a 400 pH inductor, capacitor 673 comprises a 1000pF capacitor, capacitor 674 comprises a 1000 pF capacitor, capacitor 675comprises a 400 pF capacitor, resistor 676 comprises a 1 kΩ resistor,and resistor 677 comprises a 500Ω resistor, the oscillator would run atapproximately 370 kHz. One suitable transistor 670 is the model 2N5484n-channel amplifier offered by Fairchild Semiconductor Corp., San Jose,Calif., for example. One suitable diode 671 is a model 1N4148 high-speeddiode. Capacitor 678 (e.g., a 0.01 μF capacitor) and resistor 679 (e.g.,a 1 kΩ resistor) couple the signal (e.g., a sine wave or other waveform)produced by the oscillator to the noninverting input of a poweramplifier 680, which drives the piezoelectric transducer 630. Thepiezoelectric transducer 630 may have a capacitance of 1000 pF, forexample. One suitable amplifier 680 is the model LT1210 current feedbackamplifier offered by Linear Technology, Milpitas, Calif., for example. Aresistor 681 (e.g., a 150Ω resistor) is provided between the negativeterminal of power sources 622 and 623 and the inverting input of theamplifier 680. A feedback resistor 682 (e.g., a 20 kΩ resistor) isprovided between the inverting input of the amplifier 680 and the outputof the amplifier 680. A capacitor 683 (e.g., a 0.01 μF capacitor) may beprovided between the output of the amplifier 680 and the shutdown inputof the amplifier 680.

FIG. 6E is a block diagram of an example receiver 660, which includes anamplifier 690. Non-electromagnetic compression waves that are incidentthe piezoelectric receiving transducer 640 generate a signal which isamplified by the amplifier 690. The amplified signal may then be sent toan analog to digital convertor for processing. Based on a change in thereceived signal the scale operator will be sent an alert if a correctiveaction is required. The piezoelectric transducer 640, which may have acapacitance of 100 pF, is coupled to the noninverting input of theamplifier 690. One suitable amplifier 690 is the model LT1037operational amplifier offered by Linear Technology, Milpitas, Calif.,for example. A power source 691 (e.g., 5 volts) supply the necessarypower to drive the amplifier 690. A resistor 692 (e.g., a 150Ω resistor)is provided between the negative terminal of power source 691 and theinverting input of the amplifier 690. A resistor 693 (e.g., a 100 kΩresistor) and a capacitor 694 (e.g., a 0.001 μF capacitor) are connectedin parallel between the inverting input of the amplifier 690 and theoutput of the amplifier 690.

FIG. 7 is a high-level flowchart illustrating a method 700 for reducingweighing errors associated with data readers, according to oneembodiment. Initially, one or more emitter transducers (e.g., emitter(s)500), one or more receiving transducer (e.g., sensor(s) 510), or acombination thereof, are installed in the scanner system 100 a andcommunicatively coupled to one or more of a transmitter (e.g.,transmitter 620), receiver (e.g., receiver 660), and a controller (e.g.,controller 540). For example, as shown in FIGS. 5 and 6A, an array ofemitter(s) 500 may be positioned one or more of the edges of the weighplatter 110 and one or more sensor(s) 510 may be supported on the upperhousing 124. The user or operator can then operate the scanner system ina conventional manner. For example, the user can position itemsproximate the lower window 130, the upper window 132, or both, in anattempt to read encoded symbols thereon. In addition, the user can weighitems by placing the items on the weigh platter 110.

The method 700 includes the steps of generating and transmitting one ormore non-electromagnetic compression waves from one or more emitters atstep 705. For example, a transmitter (e.g., transmitter 620) may becoupled to and drive the one or more emitter transducers so that thetransducers transmit non-electromagnetic compression waves, whichpropagate toward one or more sensors. The emitter(s) may extend alongone or more lateral edges of the weigh platter 110 (FIG. 6A), bedisposed on the upper housing 124 (FIG. 6B), or be suitably positionedelsewhere on the scanner system. After being generated, the compressionwaves travel to one or more sensors. At step 710, compression wave(s)incident upon the one or more sensors are detected. For example, areceiver (e.g., receiver 660) may be coupled to the one or more sensorsto amplify the signal generated at the sensor(s) by the incidentcompression waves. The receiver may also be coupled to an analog todigital convertor so that the received signals can be processed.

At step 715, it is determined whether an item alters one or more of thenon-electromagnetic compression waves generated by the emitter(s). Forexample, as non-electromagnetic compression waves impact the sensor(e.g., a piezoelectric film or crystal), the sensor 510 produces avoltage that is proportional to the intensity or amplitude of theincident wave. Thus, the receiver (e.g., receiver 660), the controller(e.g., controller 540), or both, may monitor the voltage across thesensor(s) (e.g., across surfaces of the piezoelectric film or crystal)to determine whether the amplitude of incident waves change over time orfrom a baseline. The method 700 may continuously or periodically monitorthe voltage across the sensor(s) for amplitude changes (e.g., changesthat exceed a threshold) or may measure the voltage across the sensor(s)in response to a weigh request and compare the measured voltage to abaseline voltage. If an item, such as the carrot 530, overlaps one ormore emitter(s) (FIG. 6A) or sensor(s) (FIG. 6B), the amplitude ofincident waves at the sensor(s) will be reduced.

According to one embodiment, the method 700 periodically measures thevoltage across the sensor(s) to update the baseline amplitude ofincident waves and stores the updated baseline amplitude in a memory(e.g., memory 250, drive 260, or both). Thus, after receiving a weighrequest, the voltage across the sensor(s) may be measured and comparedto the stored baseline amplitude to determine whether an item alters oneor more of the waves generated by the emitter(s). Periodically updatingthe baseline amplitude may help reduce the effect of contaminantscovering the emitter(s), the sensor(s), or both.

The method 700 may determine whether an item alters waves generated bythe emitter(s) in other ways. For example, according to anotherembodiment, one or more transducers configured to transmit and receivenon-electromagnetic compression waves extend along one or more lateraledges of the weigh platter 110 are disposed on the upper housing 124proximate one or more lateral edges of the weigh platter 110, or arepositioned elsewhere on the scanner system. A transmitter coupled to thetransducers drive the transducers with a signal so that the transducerstransmit non-electromagnetic compression waves from the top surface ofthe weigh platter. A receiver, controller, or both, are also coupled tothe transducers and monitor the transducers to detect compression wavesreflected by an item back toward the top surface of the weigh platter todetermine whether an item overhangs an edge of the weigh platter (i.e.,rests partially on the weigh platter and partially on the checkoutcounter or other fixed object such as a frame of the scanner). Thereceiver, controller, or both, monitor incident waves reflected by anitem within a certain distance from the transducers (e.g., based on thetime it took the wave to propagate from the transducer to the item andback to the transducer) to detect items that may affect the measuredweight of the item. In other words, the receiver, the controller, orboth, may look for waves reflected by an item positioned proximate thetransducers (which is probative of an item overhanging the weighplatter) and may ignore incident waves reflected from the ceiling or theuser's hand passing over the sensor(s).

Upon detecting an alteration of one or more of the waves, the method 700may notify the user that the item may not be accurately weighed (i.e.,an item extends between the weigh platter and another surface, such asthe counter or frame of the scanner) via the alert module 220 (FIG. 2).Additionally or alternatively, the method 700 may halt the weighingoperation until item is properly positioned (e.g., the measuredamplitude returns to within operational tolerances) via the interlockmodule 230.

Radiofrequency Scale Guard

FIGS. 8-10 illustrate another possible implementation of the scale guardmodule 210 (of FIG. 2) utilizes radio waves to determine whether an itemrests or partially rests on a surface other than the weigh platter 110,such as the counter 160 or a scanner frame 840. According to theembodiment illustrated in FIGS. 8, 9, and 10, the scale guard module 210comprises a weigh platter 110 configured to form a radiating antenna 800and a receiving antenna 810, such as a loop of wire, at least partiallysurrounding the weigh platter 110 for receiving a radiofrequency (RF)signal 820 from the radiating antenna 800. If an item being weighed,such as a carrot 830, rests partially on the weigh platter 110 andpartially on another surface (e.g., the counter 160), the RF signal(s)820 incident at the receiving antenna 810 will be altered.

The scanner system 100 c illustrated in FIG. 8 is similar to the system100 illustrated and described with reference to FIGS. 1-4, except thescanner system 100 c includes a scale guard module that utilizes radiowaves to determine whether an item being weighed rests or partiallyrests on a surface other than the weigh platter 110. Thus, the scannersystem 100 c may include any of the components illustrated and describedwith reference to FIGS. 1-4, such as the scale module 200, the interlockmodule 230, the alert module 220, and the data reader.

According to one embodiment, the radiating antenna 800 comprises theweigh platter 110. For example, the weigh platter 110 may beelectrically isolated from other portions of the scanner system 100 c,such as a scanner frame 840 or counter 160, so that the weigh platter110 forms a transducer capable of transmitting or receivingelectromagnetic waves. The radiating antenna 800 may also take otherforms. For example, the antenna 800 may comprise a length of wireembedded into the weigh platter 110 along all or a portion of theperimeter or peripheral edge 815 of the weigh platter 110. Additionally,an array of antennas may be supported by the weigh platter 110.

According to a preferred embodiment, the antenna 800 is configured totransmit (or receive) electromagnetic waves within the range ofapproximately three megahertz to approximately thirty megahertz.However, the antenna 800 may be configured to transmit (or receive)electromagnetic waves within the range of approximately three hertz toapproximately three-hundred gigahertz. The antenna 800 may beomnidirectional or configured to direct RF signal(s) 820 toward thereceiving antenna 810.

An RF transmitter 850 is provided to drive the radiating antenna 800with a signal that causes the antenna 800 to radiate one or more RFsignals 820. FIG. 9A is a block diagram illustrating an RF transmitter850, according to one embodiment. The RF transmitter 850 comprises apower source 852 and RF oscillator 854. The power source 852 suppliesthe necessary power to drive the antenna 800. Because the RF signal(s)820 may need only travel a short distance from the radiating antenna 800and receiving antenna 810, the power requirements for the RF transmitter850 are relatively modest. For example, the distance between theradiating antenna 800 and receiving antenna 810 may be approximately ¼inch and the RF transmitter 850 may have a power level of approximately100 μW. The RF oscillator 854 generates a signal having a preselectedfrequency to drive the antenna 800. For example, the signal may have afrequency within the range of approximately three megahertz toapproximately thirty megahertz. The frequency used to drive the antenna800 may be selected based on the length of the antenna (e.g., the lengthof the antenna is proportional to the drive frequency) and may betunable in the field. To maximize the power transfer from the RFtransmitter 850 to the antenna 800, the RF transmitter 850 may alsoinclude an impedance matching circuit to match the impedance of the RFtransmitter 850 and the antenna 800.

FIG. 9B is a schematic diagram of a radiofrequency transmitter 900,according to one embodiment. The RF transmitter 900 comprises atransistor 905 (the gain component) and a resonant tank circuit (formedby capacitor 910 and inductor 915) connected to the collector oftransistor 905. One suitable transistor 905 is the model 2N3904 NPNamplifier offered by Fairchild Semiconductor Corp., San Jose, Calif.,for example. The resonant tank circuit can be tuned to any number offrequencies based on Equation 1, where F_(osc) is the oscillatingfrequency, C₂ corresponds to capacitor 910 and L₁ corresponds toinductor 915.

$\begin{matrix}{F_{OSC} = \frac{1}{6.28*\sqrt{C_{2}*L_{1}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

For example, if capacitor 910 is a 100 pF capacitor and inductor 915 isa 2.5 μH inductor, the resonant frequency is approximately 10 Mhz. Theantenna 925 is connected to the output of the RF transmitter 900 at anend of inductor 915 opposite the power source 920 (e.g., a five volt DCpower source). Antenna 925 may comprise the weigh platter 110 or anappropriate length wire surrounding the weigh platter 110. Resistor 930(e.g., a 10 kΩ resistor) and capacitor 940 (a 0.01 μF capacitor) may beconnected in parallel between the base of transistor 905 and thepositive side of the power source 920. Resistor 935 (e.g., a 1 kΩresistor) may be connected between the base of transistor 905 and thenegative side of the power source 920. Resistor 945 (e.g., a 1 kΩresistor) and capacitor 950 (a 22 pF capacitor) may be connected inparallel between the emitter of transistor 905 and the negative side ofthe power source 920.

Referring again to FIGS. 8 and 10A, the receiving antenna 810 comprisesa loop of wire at least partially surrounding the weigh platter 110 toreceive the RF signal 820 from the radiating antenna 800 according toone embodiment. For example, as shown in FIG. 8, the receiving antenna810 surrounds three edges 815 of a top surface of the weigh platter 110.The receiving antenna 810 may take other forms. For example, the antenna810 may comprise a length of wire embedded into the scanner frame 840 orthe counter 160. Additionally, an array of antennas may be supported bythe scanner system 100, such as by the scanner frame 840 or the counter160, and configured to receiving the RF signal 820 from the radiatingantenna 800.

The receiving antenna 810 is configured to receive (or transmit) the RFsignal(s) 820 from the radiating antenna 800, which is, according to apreferred embodiment, within the range of approximately three megahertzto approximately thirty megahertz. However, the antenna 810 may beconfigured to receive (or transmit) electromagnetic waves within therange of approximately three hertz to approximately three-hundredgigahertz.

An RF receiver 860 is provided to monitor the receiving antenna 810 forthe RF signal(s) 820, and in particular, a change in the RF signal(s)820. FIG. 10A is a block diagram of an RF receiver 860, according to oneembodiment. The RF receiver 860 comprises a wideband filter 862, anamplifier 864, a low pass filter 866, and a comparator 868. The antenna810 is coupled to the amplifier 864 via the wideband filter 862. Thewideband filter 862 is configured to eliminate or filter out unwantedlow and high frequency signals which are outside of a preselected range.An impedance matching circuit may be provided between the antenna 810and the filter 862 for matching the impedances of the RF receiver 860and the antenna 810 in an attempt to maximize the power transfer fromthe antenna 800 to the RF receiver 860. According to a preferredembodiment, the amplifier 864 provides a gain of approximately seven dBat the center frequency of approximately ten megahertz. However, theamplifier 864 may provide a higher or lower gain.

The output from the amplifier 864 may run through the low pass filter866 to remove any high frequency noise and then be fed into thecomparator 868 along with a predetermined threshold reference voltage869. The comparator 868 then monitors the output from the low passfilter 866 for a change in voltage caused by a change in the RFsignal(s) 820 indicative of an item extending between the weigh platter110 and another surface. For example, if an item, such as the carrot830, extends between the weigh platter 110 and another surface, the itemchanges the coupling of the RF signal 820 from the radiating antenna 800to the receiving antenna 810. The RF coupling change may result in adecrease in voltage at the output of the low pass filter 866. If theoutput voltage of the low pass filter 866 drops below the thresholdvoltage 869, the comparator 868 will output a low logic signalindicating that an item extends between the weigh platter 110 andanother surface. If the item is properly positioned on the weigh platter110, the output voltage of the low pass filter 866 may rise above thethreshold voltage 869 and cause the comparator 868 to output a highlogic signal.

Alternations in the RF signal 820 caused by the item may be detected inother ways. For example, the RF coupling change caused by the item mayresult in an increase in voltage at the output of the low pass filter866 and cause the comparator 868 to output a high logical signalindicative of a potential weighing error. By way of another example, theitem may alter the RF signal 820 in other ways, such as introducing aphase shift into the signal or altering a frequency of the signal. TheRF receiver 860 may be implemented in hardware, software, firmware, orany combination thereof. Thus, the RF signal(s) 820 received by theantenna 810 may be sampled and one or more the components that comprisethe RF receiver 860 may be implemented in software, for example.

FIG. 10B is a schematic diagram of a radiofrequency receiver 1000,according to one embodiment. The RF receiver 1000 may comprise an RFamplifier section 1010, a diode pump section 1030, and a comparatorsection 1040. The RF amplifier section 1010 is a tuned amplifier whereinductor 1011 and capacitor 1012 set the bandwidth of the amplifiersection 1010. According to one embodiment, the inductor 1011 comprises a10 μH inductor and capacitor 1012 comprises a 47 pF capacitor, so theamplifier section 1010 has a center frequency of approximately 10 MHzand a passband of approximately 1 Mhz. Antenna 1020 (e.g., the weighplatter 110 or the receiving antenna 810) is connected to the junctionof inductor 1011 and capacitor 1012. The other end of capacitor 1012 isconnected to the base of transistor 1015. One suitable transistor 1015is the model 2N2222A NPN transistor offered by Philips Semiconductor,Sunnyvale, Calif., for example. Resistor 1013 (e.g., a 1.6 kΩ resistor)and capacitor 1014 (e.g., a 100 pF capacitor) are connected in parallelbetween the emitter of transistor 1015 and the negative side of powersource 1005 (e.g., a twelve volt DC source). Resistor 1016 (e.g., a 1.6kΩ resistor) and inductor 1017 (e.g., a 8 μH inductor) are connected inseries between the collector of transistor 1015 and the positive side ofthe power source 1005. A resistor 1018 (e.g., a 100 kΩ resistor) isconnected between the base of transistor 1015 and the positive side ofthe power source 1005.

The output of the RF amplifier section 1010 is coupled via a capacitor1025 (e.g., a 1 nF capacitor) to the diode pump section 1030, whichrectifies the RF signal received from the antenna 1020 and amplified bythe RF amplifier section 1010. The DC output from the diode pump section1030 is proportional to the amplitude of the RF signal received by theantenna 1020. The diode pump section 1030 comprises diodes 1031 and 1032and capacitor 1033 (e.g., a 1 nF capacitor). The anode of diode 1031 iscoupled to the negative side of the power source 1005 and the cathode iscoupled to the capacitor 1025. The anode of diode 1032 is coupled to thecapacitor 1025 and the cathode of the diode 1031 and the cathode ofdiode 1032 is coupled to the non-inverting input of comparator 1041. Thecapacitor 1033 is connected between the cathode of the diode 1032 andthe negative side of the power source 1005. Suitable diodes 1031 and1032 are the model D1N4148 diode offered by Fairchild SemiconductorCorp., San Jose, Calif., for example.

The DC output from the diode pump section 1030 is coupled to thenon-inverting input of comparator 1041. If the DC output from the diodepump section 1030 falls below the reference voltage level set byresistor 1042 and resistor 1043, the output from the comparator 1041transitions from high to low indicating that an item extends between theweigh platter 110 and another surface (e.g., the item has changed theamount of coupled RF to the antenna 1020). Thus, if the resistor 1042 isa 11.8 kΩ resistor and the resistor 1043 is a 200Ω resistor, the outputfrom the comparator 1041 transitions from high to low if the DC outputfrom the diode pump section 1030 falls below approximately 0.2 volts. Asshown in FIG. 10B, the resistor 1042 is connected between the positiveside of the power source 1005 and the inverting input of comparator 1041and resistor 1043 is connected between the negative side of the powersource 1005 and the inverting input of comparator 1041. One suitablecomparator is the model LMC7211 comparator offered by NationalSemiconductor Corp., Arlington, Tex., for example. The RF receiver 1000may include additional components, such as a capacitor 1044 (e.g., a 22μF capacitor) connected between the positive and negative sides of thepower source 1005 and a resistor 1045 (e.g., a 20 kΩ resistor) connectedbetween the positive side of the power source 1005 and the output of thecomparator 1041.

The RF transmitter (e.g., RF transmitters 850 or 900), the RF receiver(e.g., RF receiver 860 or 1000), or both, may be communicatively coupledto a controller 870, which is configured to determine whether an itemalters the RF signal 820. For example, the controller 870 may monitorthe output of the comparator 868 for a change from logic high to logiclow (or vice-versa). The controller 870 may also be configured to causethe RF transmitter 850 to start transmitting the RF signal 820 and causethe RF receiver 860 to start monitoring the antenna 810 for the RFsignal 820 and alterations thereof. The controller 870 may beincorporated into the processor 240, or may comprise a standalonecomponent, such as a commercially available processor or other logicmachine capable of executing instructions.

The radiofrequency scale guard module may be implemented in other ways.For example, the RF transmitter 850 and the RF receiver 860 may comprisea transceiver and include a switch for coupling the transceiver to theradiating antenna 800 or the receiving antenna 810. Additionally, thelocations of the radiating antenna 800 and receiving antenna 810 may bereversed. For example, the weigh platter 110 may form the receivingantenna 810 and the loop of wire may comprise the radiating antenna 800.Further, one or more radiating antennas 800, one or more receivingantennas 810, or any combination thereof, may be located in variouslocations, such as the upper housing portion 124, the fruit rail 112,the lower housing portion 122, the scanner frame 840, the counter 160,or elsewhere on the system scanner 100.

FIG. 11 is a high-level flowchart illustrating a method 1100 forreducing weighing errors associated with data readers, according to oneembodiment. Initially, one or more radiating antennas 800, one or morereceiving antennas 810, or a combination thereof, are installed on thescanner system 100 and connected to respective components, such as theRF transmitter 850, the RF receiver 860, or the controller 870.Preferably, the weigh platter 110 is configured to form the radiatingantenna 800 (e.g., by electrically isolating the weigh platter 110 fromother portions of the scanner system 100) and a loop of wire ispositioned to at least partially surround the weigh platter 110 to formthe receiving antenna 810 (see, e.g., FIG. 8). The user can then operatethe scanner system 100 in a conventional manner. For example, the usercan position items proximate the lower window 130, the upper window 132,or both, in an attempt to read encoded symbols thereon. In addition, theuser can weigh items by placing the items on the weigh platter 110.

At step 1105, the method 1100 generates and applies an RF signal to aset of radiating antennas 800 (where the set may comprise one or moreantennas), such as the weigh platter 110. At step 1110, the method 1100monitors a set of receiving antennas 810 (where the set may comprise oneor more antennas), such as a loop of wire partially surrounding theweigh platter 110, for alterations of the RF signal(s) 820 received bythe set of antennas 810. In other words, the RF receiver is looking fora change in the coupling (e.g., transfer of energy) of the RF signal(e.g., a change in the amplitude of the signal received). For example,the RF transmitter 850 may be configured to drive the set of radiatingantennas 800 with a signal that causes the set of antennas 800 toradiate the RF signal(s) 820, and the RF receiver 860 may be configuredto filter, amplify, and compare the RF signal(s) 820 received by the setof receiving antennas 810 to a predetermined threshold.

According to one embodiment, the method 1100 periodically updates thethreshold (e.g., daily). For example, the method 100 may periodicallymeasure or monitor the strength or amplitude of the RF signal when anitem does not rest partially on the weigh platter and partially on thecheckout counter or other fixed object to update the threshold. Theupdated threshold may be used to update the threshold reference voltage869 or may stored in a memory (e.g., memory 250, drive 260, or both).Periodically updating the threshold may help reduce environment effects,such as humidity, on the radiofrequency scale guard module.

At step 1115, the method 1100 determines whether an item alters the RFsignal(s) 820 transmitted by the set of radiating antennas 800. Forexample, if an item, such as the carrot 830, overlaps the set ofradiating antennas 800 and the set of receiving antennas 810, thecoupling of the RF signal between the antennas 800 and 810 will bealtered. Thus, the controller 870 may monitor the output of thecomparator 868 for logic level changes (e.g., low to high, or high tolow) indicating that the received RF signal(s) 820 have been altered bythe item in comparison to a reference signal.

Upon detecting an alteration of the RF signal(s) 820 transmitted by theset of radiating antennas 800, the method 1100 preferably notifies theuser that an item may not be accurately weighed (i.e., an extendsbetween the weigh platter 110 and another surface, such as the counteror frame of the scanner) via the alert module 220 (FIG. 2). Additionallyor alternatively, the method 1100 may halt the weighing operation untilitem is properly positioned (e.g., received RF signal returns to withinoperational tolerances) via the interlock module 230.

Light Beam Based Scale Guard

FIGS. 12A-13 illustrate another possible implementation of the scaleguard module 210 (of FIG. 2) utilizes light beams along opposing edgesof the weigh platter 110 to determine whether an item rests or partiallyrests on a surface other than the weigh platter 110, such as the counter160 or a scanner frame. FIGS. 12A and 13 illustrate the scale guardmodule 210 comprising one or more sources (e.g., sources 1200 a and 1200b) configured to transmit two substantially parallel light beams 1210 aand 1210 b along opposing lateral edges of the weigh platter 110 and oneor more sensors (e.g., sensors 1220 a and 1220 b) configured to detectreflected light beams 1212 a and 1212 b. If an item being weighed, suchas a carrot 1230, rests partially on the counter 160 and partially onthe weigh platter 110, any combination of the light beam 1210 a, thelight beam 1210 b, the reflected light beam 1212 a, or the reflectedlight beam 1212 b will be blocked or partially blocked.

The scanner system 100 d illustrated in FIGS. 12A and 13 is similar tothe system 100 illustrated and described with reference to FIGS. 1-4,except the scanner system 100 d includes a scale guard module thatutilizes light beams along opposing edges of the weigh platter 110 todetermine whether an item being weighed rests or partially rests on asurface other than the weigh platter 110. Thus, the scanner system 100 dmay include any of the components illustrated and described withreference to FIGS. 1-4, such as the scale module 200, the interlockmodule 230, the alert module 220, and the data reader.

Preferably, two sources 1200 a and 1200 b are provided for transmittingrespective light beams 1210 a and 1210 b along opposing edges of theweigh platter 110. While the sources 1200 a and 1200 b may be supportedby the upper housing 124, the sources 1200 a and 1200 b may be installedelsewhere, such as the lower housing 122 or the counter 160. Accordingto one embodiment, the sources 1200 a and 1200 b are not mounted on theweigh platter 110. Additionally, one or more mirrors may be provided(e.g., in the upper housing 124) to direct light beams 1210 a and 1210 balong opposing edges of the weigh platter 110. Thus the sources 1200 aand 1200 b need not be located in-line with the light beams 1210 a and1210 b and instead may be offset (e.g., laterally or vertically) fromthe light beams 1210 a and 1210 b if one or more redirecting mirrors areused. Further, additional or fewer sources may be provided. In a singlesource configuration, a set of N mirrors (where N≧1) may be provided tosplit the light beam produced by the source into light beams 1210 a and1210 b. For example, one or more of the mirrors may be coated with afilm, such as a metal film, having a thickness that transmits about halfof the incident light and reflects the other half. Thus, the source maydirect a light beam toward a first mirror (e.g., a half-silvered mirror)that redirects a portion of the light beam along one of the opposingedges of the weigh platter 110 and another portion of the light beam toa second mirror, which redirects the light beam along the other opposingedge of the weigh platter 110 (which may require the use of one or moreredirecting mirrors).

The sources 1200 a and 1200 b may be configured to transmit the lightbeams 1210 a and 1210 b, which may be minimally divergent as illustratedin FIG. 12B or moderately divergent as illustrated in FIG. 12C, over asurface of the weigh platter 110, a surface of the counter 160, anothersurface of the scanner system 100, or any combination thereof.Additionally, the sources 1200 a and 1200 b may be configured totransmit more than one light beam along opposing sides of the weighplatter 110 (e.g., over both the weigh platter 110 and the counter 160).If the weigh platter 110 comprises another geometric shape, such as apolygon or a circle, the sources 1200 a and 1200 b may be configured totransmit light beams along one or more of the edges of the polygon oraround all or a portion of a perimeter of the circle.

Preferably, the sources 1200 a and 1200 b comprise infrared lightemitting diodes (LEDs) emitting unmodulated electromagnetic radiationhaving a wavelength between approximately 750 nanometers andapproximately one millimeter. However, the sources 1200 a and 1200 b maycomprise other sources of light, such as an LED emitting anotherwavelength of light, a laser diode or other laser, or other suitablesources of light. Additionally, the light source 440 of the laser basedscanner 190 may be directed using one or more lasers along opposingedges of the weigh platter 110.

A set of mirrors are positioned on an edge of the weigh platter 110opposite the sources 1200 a and 1200 b and are configured to reflect thelight beams 1210 a and 1210 b in a direction toward the sources 1200 aand 1200 b, but at an angle θ above (or below) the light beams 1210 aand 1210 b. For example, mirrors 1240 a and 1240 b may be supported onor embedded in the fruit rail 112. The angle θ may vary depending on theparticular scanner system 100. For example, the angle θ may be selectedsuch that reflected light beams 1212 a and 1212 b enter the upperhousing 124 anywhere from slightly above the light beams 1210 a and 1210b to slightly below the top of the upper housing 124.

Having the reflected light beams 1212 a and 1212 b travel toward thesensors 1220 a and 1220 b at an angle θ above the light beams 1210 a and1210 b allows the sensors 1220 a and 1220 b to be supported on upperhousing 124, without sending a light beam along a fruit rail edge of theweigh platter 110. If the light beam traveled between mirrors 1240 a and1240 b, an item resting on the fruit rail 112 (and entirely resting onweigh platter 110) may falsely indicate that weighing error hasoccurred. In addition, the system may be easier to align and be lesssusceptible to misalignment during use if the mirrors 1240 a and 1240 bneed only be directed toward sensors 1220 a and 1220 b instead of alsobe aligned with each other. Further, having the reflected light beams1212 a and 1212 b travel toward the sensors 1220 a and 1220 b at anangle θ above (or below) the light beams 1210 a and 1210 b allows alarger area to be monitored (e.g., a taller item that overhangs scalemay not block light beams 1210 a or 1210 b, but may block reflectedbeams 1212 a or 1212 b and thus detect a possible weighing error). Thus,having the reflected light beams 1212 a and 1212 b travel toward thesensors 1220 a and 1220 b at an angle θ above (or below) the light beams1210 a and 1210 b helps ensure that possible weighing errors will bedetected if items overhang the scale and contact the counter but do notblock the lower beam (e.g., carrots with leafy stems).

In a preferred configuration, the sensors 1220 a and 1220 b comprisephototransistors configured to detect infrared light having a wavelengthbetween approximately 750 nanometers and approximately one millimeter.However, the sensors 1220 a and 1220 b may comprise other suitablephotodetectors capable of converting light into voltage or current, suchas a phototransistor configured to detect other wavelengths, aphotodiode, or a transducer that both emits and detects light. WhileFIG. 12A illustrates the sensors 1220 a and 1220 b installed in theupper housing 124, the sensors 1220 a and 1220 b may be installedelsewhere, such as the lower housing 122 or the counter 160.Additionally, one or more mirrors may be provided in the upper housing124 to redirect the reflected light beams 1212 a and 1212 b toward thesensors 1220 a and 1220 b (so that the sensors 1220 a and 1220 b do notneed to be in-line with the reflected light beams 1212 a and 1212 b).

A controller 1250 may be communicatively coupled to the sources 1200 aand 1200 b, the sensors 1220 a and 1220 b, or a combination thereof, andbe configured to determine whether an item blocks or partially blocksany of the light beams 1210 a or 1210 b or reflected light beams 1212 aor 1212 b. For example, the controller 1250 may monitor an output of thesensor 1220 a, the sensor 1220 b, or both, for a voltage above or belowa certain threshold (i.e., the threshold may be selected to indicate anamount of light incident upon the sensor that indicates that an itempartially rests on a surface other than the weigh platter 110). Forexample, if an item, such as the carrot 1230 blocks or partially blocksthe light beam 1210 a, the output of the sensor 1220 a may drop below acertain threshold voltage. If the item is repositioned so that it nolonger blocks a light beam, the output of the sensor 1220 a may riseabove the threshold voltage indicating that an item no longer partiallyrests on a surface other than the weigh platter 110. The controller 1250may be incorporated into the processor 240, or may comprise a standalonecomponent, such as a commercially available processor or other logicmachine capable of executing instructions.

One or more of light beams 1210 a, 1210 b, 1212 a, and 1212 b may beminimally divergent as illustrated in FIG. 12B or moderately divergentas illustrated in FIG. 12C. The divergence of light beams 1210 a, 1210b, 1212 a, and 1212 b may be a function of the sources 1200 a and 1200 b(i.e., the source may produce a light beam that is minimally divergentor moderately divergent) or one or more lenses may be provided in alight path proximate the source to control the divergence. According toa preferred embodiment, the one or more lenses are convex lenses, butthe one or more lenses may be spherical, cylindrical,sphero-cylindrical, or aspheric, for example, in which one or moresurfaces is convex, concave, or planar. A cylindrical lens may, forexample, help create a more vertical planar pattern.

With reference to FIG. 12B, the light source 1200 c (which may besimilar or identical to the sources 1200 a and 1200 b) is configured totransmit a minimally divergent light beam 1210 c. For example, theminimally divergent light beam 1210 c may have a beam width that isbetween approximately two degrees and approximately five degrees for thelength of the beam's travel (e.g., the light beam 1210 c may becollimated, much like a focused LASER beam). As described with referenceto FIGS. 12A and 13, the minimally divergent light beam 1210 c isdirected to a reflective surface (e.g., mirror 1240 b), which may be amirror or other reflective element, and then reflected by the reflectivesurface. The reflected light beam 1212 c is directed by the reflectivesurface toward a sensor 1220 c (which may be an IR receiver or othersuitable sensor, such as a sensor similar or identical to the sensors1220 a and 1220 b). The source 1200 c and reflective surface produce twodistinct beams 1210 c and 1212 c. If the minimally divergent light beam1210 c, the reflected light beam 1212 c, or both, are interrupted by anobject or item that extends beyond an edge of the weigh platter surface,the sensor 1220 c (which may be coupled to the controller 1250)indicates an off-scale or fault condition (i.e., an item extends betweenthe weigh platter 110 and another surface, such as the counter or frameof the scanner). Thus the sensor 1220 c, the controller 1250, or both,may monitor an amount of light incident the sensor 1220 c (and possiblycompare the detected amount of light to a threshold) to determinewhether an item rests or partially rests on a surface other than theweigh platter 110.

With reference to FIG. 12C, the light source 1200 d (which may besimilar or identical to the sources 1200 a and 1200 b) is configured totransmit a moderately divergent light beam 1210 d (the divergence oflight beam 1210 d is not to scale and is exaggerated for illustrationpurposes). For example, the moderately divergent light beam 1210 d mayhave a beam width that is between approximately ten degrees andapproximately 120 degrees for the length of the beam's travel (e.g., themoderately divergent light beam 1210 d diverges relatively quickly alongits path of travel). As described with reference to FIGS. 12A and 13,the moderately divergent light beam 1210 d is directed to a reflectivesurface (e.g., mirror 1240 b), which may be a mirror or other reflectiveelement, and then reflected by the surface. The reflected light beam1212 d is directed by the reflective surface toward a sensor 1220 d(which may be an IR receiver or other suitable sensor, such as a sensorsimilar or identical to the sensors 1220 a and 1220 b). The source 1200d and reflective surface produce two distinct beams 1210 d and 1220 d.If the moderately divergent light beam 1210 d, the reflected light beam1212 d, or both, are interrupted by an object or item that extendsbeyond an edge of the weigh platter surface, the sensor 1220 d (whichmay be coupled to the controller 1250) indicates an off-scale or faultcondition (i.e., an item extends between the weigh platter 110 andanother surface, such as the counter or frame of the scanner). Thus thesensor 1220 d, the controller 1250, or both, may monitor an amount oflight incident the sensor 1220 d (and possibly compare the detectedamount of light to a threshold) to determine whether an item rests orpartially rests on a surface other than the weigh platter 110. One ormore lenses 1260 may be provided to focus the reflected light beam 1212d onto the sensor 1220 d. According to a preferred embodiment, the oneor more lenses are convex lenses, but the one or more lenses may bespherical, cylindrical, sphero-cylindrical, or aspheric, for example, inwhich one or more surfaces is convex, concave, or planar. One possibleadvantage of using a moderately divergent light beam is that unlike thefocused beam (e.g., of IR) of the minimally diverge light beam, thelight (of the moderately divergent beam) diverges relatively quicklyalong its path and helps form a wider field of detection of an off-scaleobject or item.

According to one embodiment, a system for reducing weighing errorsassociated with data readers equipped with a weigh platter comprises asource configured to transmit two parallel light beams along opposingedges of the weigh platter, a set of mirrors positioned on an edge ofthe weigh platter opposite the source and configured to reflect the twoparallel light beams in a direction toward the source at an angle abovethe light beams, a sensor configured to detect the reflected lightbeams, and a controller communicatively coupled to the detector, thecontroller configured to determine whether an item extends between theweigh platter and another surface by monitoring the sensor for anindication that any of the light beams have been interrupted. The sourceand the sensor are preferably supported on the vertical section of thesystem, which rising from an edge of the weigh platter extending betweenthe opposing edges. The source preferably comprises two light emittingdiodes emitting unmodulated electromagnetic radiation having an infraredwavelength and the sensor preferably comprises two photodiodesconfigured to detect unmodulated electromagnetic radiation having aninfrared wavelength. The set of mirrors are preferably supported on afruit rail that is positioned on an edge of the weigh platter oppositethe source. An interlock component that is communicatively coupled tothe controller is preferably provided and configured to disable a weighfunction associated with the weigh platter when the controllerdetermines that at least one of the light beams have been interrupted.In addition, external indicia are preferably provided to notify anoperator that an item may not properly be weighed.

FIG. 14 is a high-level flowchart illustrating a method 1400 forreducing weighing errors associated with data readers, according to oneembodiment. Initially, one or more sources, one or more sensors, one ormore mirrors or reflectors, or a combination thereof, are installed inthe scanner system 100 and communicatively coupled to the controller1250. For example, as shown in FIGS. 12A and 13, the sources 1200 a and1200 b and the sensors 1220 a and 1220 b may be supported on the upperhousing 124. The user can then operate the scanner system 100 in aconventional manner. For example, the user can position items proximatethe lower window 130, the upper window 132, or both, in an attempt toread encoded symbols thereon. In addition, the user can weigh items byplacing the items on the weigh platter 110.

At step 1405, parallel light beams are generated and transmitted alongopposing edges of the weigh platter 110, and then at step 1410 the lightbeams are reflected (assuming the light beams have not been interrupted)in a direction toward the source at an angle above the light beams. Inone example, the sources 1200 a and 1200 b may be configured to transmitlight beams 1210 a and 1210 b along opposing edges of the weigh platter110. The mirrors 1240 a and 1240 b may then reflect the light beams 1210a and 1210 b in a direction toward the sources 1200 a and 1200 b at anangle θ above (or below) the light beams 1210 a and 1210 b to formreflected light beams 1212 a and 1212 b.

At step 1415, the method 1400 determines whether an item interrupts anyof the light beams. For example, the controller 1250 may monitor thevoltage (or current) generated by sensors 1220 a and 1220 b to determinewhether an item interrupts any of the light beams 1210 a, 1210 b, 1212a, or 1212 b. Upon detecting an interruption of one or more light beams,the method 1400 may notify the user that an item may not be properlyweighed (i.e., an item extends between the weigh platter 110 and anothersurface, such as the counter or frame of the scanner) via the alertmodule 220 (FIG. 2). Additionally or alternatively, the method 1400 mayhalt the weighing operation until item is properly positioned via theinterlock module 230.

Perimeter Pattern Scale Guard

FIG. 15-22 illustrate another possible implementation of the scale guardmodule 210 (of FIG. 2) utilizes a portion of a scan field of an opticalcode reader to scan a set of patterns extending along opposing edges ofthe weigh platter 110 to determine whether an item rests or partiallyrests on a surface other than the weigh platter 110, such as the counter160 or the scanner frame. For example, the scale guard module 210 maycomprise a set of instructions for scanning reference patterns 1500 aand 1500 b extending along opposing edges of the weigh platter 110 usingan optical code reader or data reader of the scanner system 100 e. Thus,the scale guard module 210 may be stored along with the applications 254and other components 255 in memory 250, drive 260, or both. According toa preferred embodiment, an optical code reader in the upper housingportion 124, such as the imaging based scanner 180 a or the laser basedscanner 190 a, attempts to detect the reference patterns 1500 a and 1500b as illustrated by scan planes 1510 a and 1510 b in FIG. 15. As will bedescribed in more detail below, if an item being weighed rests partiallyon the counter 160 or other fixed object and partially on the weighplatter 110, all or a portion of the reference pattern 1500 a, thepattern 1500 b, or both, will be blocked, which will alter the patternread by the optical code reader. In other words, it is possible todetermine whether an item rests partially on the checkout counter orother fixed object and partially on the weigh platter based on whetherthe item blocks a portion of the light that would otherwise reflect offa region proximate a lateral edge of the checkout counter surface orother fixed object.

The scanner system 100 e illustrated in FIG. 15 is similar to the system100 illustrated and described with reference to FIGS. 1-4, except thescanner system 100 e includes a scale guard module that utilizes aportion of a scan field of an optical code reader to determine whetheran item being weighed rests or partially rests on a surface other thanthe weigh platter 110. Thus, the scanner system 100 e may include any ofthe components illustrated and described with reference to FIGS. 1-4,such as the scale module 200, the interlock module 230, the alert module220, and the data reader.

FIG. 16 is a high-level flowchart illustrating a method 1600 forreducing weighing errors associated with data readers, according to oneembodiment. At step 1605, a set of N patterns (where N≧1) are positionedalong one or more edges of the weigh platter 110. For example, as shownin FIG. 15, patterns 1500 a and 1500 b may be positioned along opposingedges of the weigh platter 110. The user can operate the scanner system100 equipped with the set of patterns in a conventional manner. Forexample, the user can position items proximate the lower window 130, theupper window 132, or both, in an attempt to read encoded symbolsthereon. In addition, the user can weigh items by placing the items onthe weigh platter 110.

As will be described in more detail below, the set of patterns extendingalong one or more edges of the weigh platter are scanned at step 1610.Based on the scan, the method 1600 determines whether an item extendsbetween the weigh platter and another surface at step 1615. According toa preferred embodiment, a portion of a scan field of an optical codereader is used to scan the set of patterns extending along opposingedges of the weigh platter 110. Thus, any optical code reader, such asthe imaging based scanner 180 or the laser based scanner 190, may beused to implement one or more of the steps of the method 1600.

For an imaging based scanner, a portion of the imaging sensor's field ofview may be used to scan the set of patterns extending along opposingedges of the weigh platter. For example, the method 1600 may read orassemble samples or pixels from the imager 330 lying along one or morelines across the image to form a desired scan pattern. The one or morelines may be oriented at any angle with respect to one another andpreferably coincide with a main line of extent of each pattern in theset of patterns.

In addition, a set of N mirrors (where N≧1) may be provided andconfigured to align a portion of the imaging sensor's field of view witheach pattern such that the scan plane associated with each pattern risesorthogonally from the surface of the weigh platter and extends along amain line or axis of extent of the pattern (see, e.g., auxiliary scannerviews 1730 a and 1730 b of FIG. 17). In other words, the set of mirrorsis configured to redirect a portion of the imaging sensor's field ofview so that the portion of the field of view is in-line with thepattern (e.g., the portion of the field of view is looking straight atthe pattern). According to one embodiment, the set of mirrors arepositioned in the upper housing 124 and comprise final redirectingmirrors and intermediate redirecting mirrors interposed between thefinal redirecting mirrors and the imager 330. The final redirectingmirrors are positioned on opposing sides of the weigh platter such thatthe final redirecting mirrors lie in same plane as the scan planeassociated with the respective platter pattern. For example, one finalredirecting mirror may be positioned in the upper housing 124 behindupper window 132 (see FIG. 15) and lie in the same plane as the scanplane 1510 a and another final redirecting mirror may be positioned inthe upper housing 124 behind upper window 132 and lie in the same planeas the scan plane 1510 b. Thus, the final redirecting mirrors redirectthe respective scan planes (e.g., scan planes 1510 a and 1510 b) towardthe imager 330. The intermediate redirecting mirrors are positionedbetween the final redirecting mirrors and the imager 330 to direct therespective scan planes onto the imager 330.

For a laser based scanner, a portion of the laser scanner's scan arc maybe used to scan the set of patterns extending along opposing edges ofthe weigh platter. For example, a set of N mirrors (where N≧1), such asone or more of the pattern mirrors 460 (FIG. 4), may be positioned inthe upper housing 124, the lower housing 122, or elsewhere on thescanner system 100 such that the set of mirrors intercept and redirect aportion of the scan arc to traverse each pattern in the set of patterns.Preferably, the set of N mirrors are configured such that a scan line(e.g., scan lines 462) formed by a respective mirror coincides with amain line of extent of each pattern in the set of patterns. In otherwords, the set of mirrors reside in locations that allow the scannersystem 100 to “view” each pattern in the set of patterns along a mainaxis of extent of the pattern. According to one embodiment, the mirrorson either side of the platter that perform the final redirections ofportions of the scan arc prior to exiting the housing essentially lie inthe same planes as the scan arcs used to scan the respective platterpatterns. Additionally, one or more intermediate mirrors may beinterposed between the beam oscillator (e.g., the rotating polygon) andthe final mirrors to direct the scanning arc to the final mirrors.

If an item extends between the weigh platter and another surface, all ora portion of at least one of the patterns in the set of patterns will beobscured by the item (see, e.g., FIG. 18). Thus, the set of patterns maybe read to determine whether any of the patterns are at least partiallyblocked and thus whether an item extends between the weigh platter andanother surface. A suitable technique may then be used to determinewhether any of the patterns are at least partially blocked. For example,a controller, such as processor 240, may be communicatively coupled toone or more of the optical code readers (e.g., imaging based scanner 180or laser based scanner 190) and configured to recognize whether thepattern read by the optical code reader indicates that an item bridgesthe weigh platter and another surface.

For a laser based scanner, a photodetector (e.g., photodetector 410 ofFIG. 4) converts light reflected from the scanned pattern into a signalindicative of the relatively dark and the relatively light portions ofthe pattern (e.g., peaks and valleys corresponding to dark and lightportions). Analog or digital techniques may then be used to process thesignal output from the photodetector 410 in order to determine whetheran item at least partially blocks any of the patterns.

For example, a filter tuned to the frequency of the pattern (see, e.g.,FIG. 22) may be provided and monitored to determine whether the filterdetects the frequency of the pattern. If an item blocks one of thepatterns, the filter will not detect the frequency of the pattern for atleast a portion of the scan arc. Thus, the controller could monitor theoutput of the filter to see whether the filter detects the frequency ofthe pattern over the relevant portion of the scan arc. The filteredsignal may also be processed to count a total number of pulses (e.g.,using edge detector 480) or to detect missing pulses (e.g., using amissing-pulse module activated when the patterns are being scanned). Forexample, as shown in FIG. 15, eighteen edges should be detected uponscanning the patterns 1500 a or 1500 b. If fewer than the expectednumber of edges (e.g., eighteen for patterns 1500 a or 1500 b) aredetected, it may be inferred that an item is blocking a portion of thepattern. By way of another example, pulses indicative of edgetransitions may be expected at certain points in the scan arc. If apulse is detected unexpectedly or not detected when expected, it may beinferred that an item is blocking a portion of the pattern. Othertechniques may be used and may be implemented digitally (e.g., bysampling the signal output from the photodetector).

Additionally, any of the above techniques for determining whether anitem at least partially blocks any of the patterns may be implementedusing an imaging based scanner. For example, after the user places anitem to be weighed, such as apple 1710, on the weigh platter 110, animaging based scanner, such as the imaging based scanner 180 a (FIG. 2),or an imaging system, such as an imaging system supported by the upperhousing section 124 or positioned some distance above weigh platter 110and coupled to the scanning system 100 e, captures an image of the weighplatter 110. FIG. 17 illustrates an example image captured where neitherof patterns 1700 a and 1700 b extending along opposing edges of theweigh platter 110 are obstructed by the apple 1710. FIG. 18 illustratesan example image captured where the apple 1710 blocks a portion of thepattern 1700 a.

After an image of the weigh platter 110 has been captured, the method1600 can attempt to read the patterns 1700 a and 1700 b to determinewhether either of the patterns 1700 a and 1700 b are at least partiallyblocked. For example, a virtual scan line extraction module may read orassemble samples or pixels from an imager lying along one or more lines(e.g., virtual scan lines 1720 a and 1720 b) corresponding to thepatterns 1700 a and 1700 b. After the appropriate data along the one ormore lines has been collected, the data is then analyzed to determinewhether any patterns are at least partially blocked. For example, thedata can be processed to locate edges (e.g., by identifying transitionsfrom one set of pixels to another set of pixels) to determine, forexample, whether or not an expected number of edges are present. Withreference to FIG. 17, each of the patterns 1700 a and 1700 b comprisefourteen dark rectangles (one of which is blocked by auxiliary scannerviews 1730 a and 1730 b). Thus, twenty-eight edges should be located,assuming an item, such as the apple 1710, is not blocking a portion ofthe pattern. However, as shown in FIG. 18, the apple 1710 blocks roughlyhalf of the dark rectangles. Thus, upon processing the data associatedwith the virtual scan line 1720 a, the total number of edge transitionswould be less than expected, and the method 1600 could alert theoperator that an item may not be accurately weighed.

Other techniques may be used to determine whether either of the patterns1700 a and 1700 b are at least partially blocked. For example, a set ofN mirrors (where N≧1) may be provided and configured to redirect aportion of the imaging sensor's field of view so that the portion of thefield of view is in-line with the pattern (e.g., the portion of thefield of view is looking straight at the pattern), as illustrated byauxiliary scanner views 1730 a and 1730 b. The patterns 1700 a and 1700b are illustrated vanishing toward a point in the auxiliary scannerviews 1730 a and 1730 b, which are exaggerated for illustrationpurposes. An image of the auxiliary scanner views 1730 a and 1730 b maythen be captured, so that the method 1600 can attempt to read thepatterns 1700 a and 1700 b to determine whether either of the patterns1700 a and 1700 b are at least partially blocked. For example, a virtualscan line extraction module may read or assemble samples or pixels froman imager lying along virtual scan lines 1740 a and 1740 b and analyzethe appropriate data along the virtual scan lines 1740 a and 1740 b todetermine whether any patterns are at least partially blocked (asillustrated in FIG. 18).

Additionally, the captured image of the weigh platter 110, the auxiliaryscanner views (e.g., 1730 a and 1730 b), or both, may be processed usingother two-dimensional image processing techniques, such as backgroundsubtraction, contrast enhancement, and reference image differencing todetermine if the perimeter patterns are fully in view or at leastpartially blocked.

Upon determining that at least a portion of one of the patterns ispartially blocked by an item, the method 1600 may notify the user thatan item may not be accurately weighed (i.e., an item extends between theweigh platter 110 and another surface, such as the counter or frame ofthe scanner) via the alert module 220. Additionally or alternatively,the method 1600 may halt the weighing operation until item is properlypositioned via the interlock module 230.

Factors, such as dirt, spills, wear, or damage, may change the patternover time or otherwise change what a reader captures as the pattern.Thus, the method 1600 may operate within fixed or adjustable operationaltolerances to effectively ignore small imperfections caused by changesto the pattern over time. Additionally, other techniques may be usedhelp prevent false positives (e.g., an incorrect determination that anitem spans the weigh platter and another surface) caused by changes tothe pattern over time, such as signal tracking and automated detectionthreshold adjustment. For example, the relatively light portions may become darker if dirt collects over a portion of the pattern. Thus, thethreshold used to signify an edge transition (e.g., a light-to-darktransition or dark-to-light transition) may automatically adjust overtime in response to incremental changes to the signal resulting fromscans of pattern over time.

The set of patterns positioned along opposing edges of the weigh platter110 may be of any suitable form and preferably one that is easilyrecognizable by the optical code reader. For example, the set ofpatterns may comprise a repeating high contrast pattern (e.g., from thescanner's perspective) that provides a readily identifiable indicationof whether or not the scan planes 1510 a and 1510 b are broken by itemsextending between the weigh platter 110 and another surface. Aspreviously described, if an item extends between the weigh platter 110and another surface (see, e.g., FIG. 18), a portion of the pattern willbe obscured from the optical code reader and will alter a signalgenerated by the optical code reader.

According to a preferred embodiment, the set of patterns comprise highoptical contrast patterns with respect to the optical reader that areminimally affected by wear caused by items being dragged across theweigh platter surface over time so that the optical reader generates asignal having a relatively high signal-to-noise ratio. For example, theset of patterns may comprise a series of holes extending through theweigh platter 110. The unbroken areas of surface of the weigh platter110 can provide the relatively light portions of the pattern (e.g., thebright or high portions) and the holes piercing the surface of the weighplatter 110 can provide the relatively dark portions of the pattern (thedark or low portions) because little or no light will be reflected bythe holes. Additionally, if the holes are of sufficient size andcompletely pierce the surface of the weigh platter 110, the holes mayprovide extra drainage for spills and may be relatively easy to keepdebris free so that the high contrast pattern can be preserved aftermany hours of use. Additionally, the surface of the weigh platter 110may be brushed (or sanded) in a direction parallel to item flow duringscanning to create a plurality of random reflective facets oriented toreflect light back toward the optical reader. As items are slid in adirection parallel to the facets of the brushed surface, the directionalreflective characteristics of the brushed surface may be preservedinstead of removed.

Variations may be made to the series of holes extending through theweigh platter and the set of patterns may take other forms. For example,a contrasting material may be positioned in or below the holes. Thecontrasting material may help create the dark portions or may comprise amaterial having a higher reflectivity than the surface of the weighplatter. Additionally, while the holes may be rectangular, the holes maycomprise any shape and may be of any size.

Instead of (or in addition to) extending through the surface of theweigh platter, the set of patterns may comprise an alternating patternof depressions and relatively flat surfaces, an alternating pattern ofprotuberances and relatively flat surfaces, or any combination thereof(e.g., alternating pattern of depressions and protuberances). Thedepressions may comprise stamped depressions, hollows, or otherconcavities. The protuberances may comprise bulges, humps, or otherprojections. For example, the set of patterns may comprise a series ofconvex stamped hemispherical features, concave stamped hemisphericalfeatures, or both. The hemispherical surface helps ensure that somelight emanating from the optical code reader (e.g., via illuminationsource 310 of FIG. 3) is reflected back toward the optical code readerin the form of a glow or bright highlight somewhere on the hemisphericalsurface. The features may take another shape, such as a paraboloid orhyperboloid. Additionally, the set of patterns may comprise anyundulating surface pattern that causes light to be reflected back towardthe optical code reader and away from the optical code reader in analternating pattern.

The set of patterns may also comprise chemically blackened, painted,screened, or other darkening procedure applied to areas of the weighplatter 110. The darkened areas may be depressed to lessen wear, may beflush with a wear resistant coating, or any combination thereof.Additionally, the set of patterns may comprise adhesive backed labelsincluding any pattern of relatively light or dark portions. Further,areas of retroreflective material may be used for the relatively lightportions and a lack of the retroreflective material may be used for therelatively dark portions.

According to yet another embodiment, the set of patterns comprises a setof lights that underlie or are embedded into the surface of the weighplatter so that light is directed toward the optical code reader. Forexample, as described with reference to FIGS. 17 and 18 of U.S.Provisional Application No. 61/267,376, filed Dec. 7, 2009, a lightguide may be disposed below the weigh platter 110 in a lower weighplatter section. One or more light sources may be disposed in the upperhousing section 124 next to the edge of the weigh platter 110 and alight guide or light pipe is provided to carry visible illumination fromthe source or sources along the edges of the weigh platter 110. Thelight guide may have a rectangular, circular or other suitable crosssection. The top surface of the light guide is modified to allow acertain amount of light to leak out along the guide's length. Thistreatment of the top surface may be surface roughening, small repeatedfaceting, or other patterning or openings to control light leakage alongthe length of the light guide. A desirable characteristic of the surfacetreatment is that the amount of light that leaks along the guide'slength at any point is approximately the same, thus making the perimeterpattern's visible illumination approximately uniform along the entirelength. Openings in the opaque surface of the weigh platter 110 allowthe leaked light to be visible.

According to still another embodiment, the set of patterns may comprisea plurality of features (e.g., one or more of a series of holesextending through the weigh platter, alternating pattern ofprotuberances and relatively flat surfaces, chemically blackened,painted, screened areas, areas of retroreflective material, and a set oflights that underlie or are embedded into the surface of the weighplatter) for making the relatively light and dark portions. Having morethan one type of the feature provides redundancy so that the pattern maybe detected under a variety of conditions and by a variety of opticalcode readers. Additionally, the set of patterns may be made up of one ormore portions of features, each of which includes a distinct feature(e.g., a portion of the pattern that is further away from the opticalcode reader may comprise a different feature to facilitate detection).

The set of reference patterns may be incorporated, positioned, orincluded on the weigh platter 110 along a lateral edge (as shown in FIG.15), the counter 160, a frame of the scanner system 100 e, elsewhere onthe scanner system 100 d, or any combination thereof. The referencepattern is preferably or would be most conveniently positioned on thetop surface of the weigh platter itself, in a region proximate thelateral edge. Alternately, the reference pattern may be positioned onthe frame of the scanner-scale proximate the lateral edge of the weighplatter. Alternately, the reference pattern may be positioned on thesurface of the checkout counter, again proximate the lateral edge of theweigh platter. Each of these three locations (on the platter, on theframe of the scanner-scale, on the checkout counter) is still in theregion proximate the lateral edge of the weigh scale. Additionally, aset of reference patterns may be installed proximate a fruit-rail edgeof the weigh platter 110. If the weigh platter 110 comprises anothergeometric shape, such as a polygon or a circle, the set of patterns maybe installed along one or more of the edges of the polygon or around allor a portion of a perimeter of the circle. Additionally, multiple setsof patterns may be provided one or more lateral edges of the weighplatter 110.

The set of patterns may comprise a regularly spaced pattern (e.g., aconstant spatial frequency), such as the patterns 1900 a and 1900 billustrated in FIG. 19. However, the regularly spaced pattern may appearunevenly spaced due to a scan angle of the optical code reader along thelength of the pattern (see, e.g., the auxiliary scanner views 1730 a and1730 b). Thus, the pattern frequency can be varied along its length asshown in FIG. 20 (e.g., a varying spatial frequency) so that whenpatterns 2000 a and 2000 b are scanned, the resulting signal comprises aconstant frequency (which may reduce the signal processing burden). Forexample, FIG. 21 illustrates an example signal 2100 resulting from ascan of the pattern 1900 a, pattern 1900 b, or both, at an arbitraryscan angle. FIG. 22 illustrates an example signal 2200 resulting from ascan of the pattern 2000 a, pattern 2000 b, or both.

One possible advantage of the perimeter pattern scale guard is thatexisting systems may easily be upgraded in the field by providing theuser with the set of patterns, such as a set of adhesive backed labelsor a replacement weigh platter 110 including the set of patterns, and ascale guard module 210 (e.g., stored on a machine-readable medium)comprising a set of instructions for scanning the set of patternsextending along opposing edges of the weigh platter 110 using a portionof the optical code reader's scan field. After the user installs the setof patterns and the scale guard module 210, the scanner will monitor theedges of the weigh platter to determine whether an item might not beproperly weighed. Part of the installation process might includeidentifying a particular make and model of scanner, so that the scaleguard module can access a data table including approximate locations ofthe edges of the weigh platter within the imager's field of view. Inaddition, part of the installation process might include steps to locatethe set of patterns within the field of view. For example, even thoughthe user may be instructed to install the set of patterns apredetermined distance from the edges, the set of patterns may notappear in the field of view where expected. Thus, the scale guard modulemay search within the imager's field of view to locate the set ofpatterns within operational tolerances (e.g., using a sum of absolutedifferences calculation between the pixels within the imager's field ofview and an expected representation of the set of patterns within thefield of view).

Edge Vision Scale Guard

FIGS. 23-25 illustrate another possible implementation of the scaleguard module 210 (of FIG. 2) utilizing an imaging based scanner tocapture an image of opposing edges of the weigh platter 110 to determinewhether an item rests or partially rests on a surface other than theweigh platter 110, such as the counter 160 or a scanner frame. Forexample, the scale guard module 210 may comprise a set of instructionsfor capturing an image of the weigh platter 110, or edges thereof, andcomparing the captured image to a reference image. Thus, the scale guardmodule 210 may be stored along with the applications 254 and othercomponents 255 in memory 250, drive 260, or both. According to apreferred embodiment, an optical code reader in the upper housingportion 124, such as the imaging based scanner 180 a, is used to capturethe image. As will be described in more detail below, if an item beingweighed rests partially on the counter 160 and partially on the weighplatter 110, the captured image will vary in a determinable manner fromthe reference image along all or a portion of edges of the weigh platter110.

FIG. 23 is a high-level block diagram of the scanner system 100 fincluding an imager 2300 communicatively coupled to a processor 2310.The imager 2300 is configured to capture an image of the weigh platter110 and the counter 160 (or another surface that surrounds or partiallysurrounds the weigh platter 110). Because scale guard module 210attempts to determine whether an item being weighed rests partially onthe counter 160 and partially on the weigh platter 110, the imager 2300may capture an image only of areas or regions of interest 2320 a, 2320b, or both, proximate a lateral edge of the weigh platter 110, whichincludes edges 2330 a, 2330 b, or both, over which an item being weighedmight lie. The images of the areas of interest 2320 a and 2320 b may beobtained in other ways, such as pulling only data corresponding to theareas of interest 2320 a and 2320 b from the imager 2300 or otherwisefiltering or masking image data from the imager 2300.

The imager 2300 may comprise the imaging based scanner 180 (e.g., theimaging based scanner 180 a in the upper housing 124) or may comprise aseparate imager or imaging system for capturing an image of an object(e.g., a CCD or CMOS digital camera) along with any associated optics.The separate imaging system may be supported by the upper housingsection 124 or positioned some distance above weigh platter 110 andcoupled to the scanning system 100 f. Likewise, the processor 2310 maycomprise the processing unit 240 or any other suitable commerciallyavailable processor or logic machine capable of executing instructions.

The processor 2310 is configured to compare one or more captured imagesto one or more reference images. If no item overlaps either of theopposing edges 2330 a or 2330 b, the captured image should be identicalto or similar to the reference image. However, if an item overlaps oneof the opposing edges 2330 a or 2330 b, the captured image will differfrom the reference image. In other words, the processor is configured todetermine whether an item rests partially on the checkout counter orother fixed object and partially on the weigh platter based on whetherthe item blocks a portion of the light that would otherwise reflect offof a region proximate the lateral edge of the top surface of the weighplatter (or a region proximate the lateral edge of the top surface ofthe checkout counter or other fixed object). FIG. 24 illustrates anexample image captured where an item, such as carrot 2400, blocks theedge 2330 a. According to one embodiment, a set of N mirrors (where N≧1)are provided and configured to redirect a portion of the image sensor'sfield of view so that the portion of the field of view is in-line withthe opposing edges 2330 a or 2330 b (e.g., the portion of the field ofview is looking straight at the edges), as illustrated by auxiliaryscanner views 2410 a and 2410 b. The mirrors may be configured tocoincide with the areas of interest 2320 a and 2320 b, so that onlyimage data corresponding to auxiliary scanner views 2410 a and 2410 bneeds to be captured.

The scanner system 100 f illustrated in FIG. 23 is similar to the system100 illustrated and described with reference to FIGS. 1-4, except thescanner system 100 f includes a scale guard module that utilizes animaging based scanner to capture an image of opposing edges of the weighplatter 110 to determine whether an item being weighed rests orpartially rests on a surface other than the weigh platter 110. Thus, thescanner system 100 f may include any of the components illustrated anddescribed with reference to FIGS. 1-4, such as the scale module 200, theinterlock module 230, the alert module 220, and the data reader.

FIG. 25 is a high-level flowchart illustrating a method 2500 forreducing weighing errors associated with data readers, according to yetanother embodiment. Initially, the imager is positioned such that one ormore edges of the weigh platter (e.g., opposing edges 2330 a and 2330 b)are within the field of view of the imager. For example, the imagingbased scanner 180 a or another imager may be supported on the upperhousing 124. Additionally, the set of N mirrors may be provided andconfigured to redirect a portion of the image sensor's field of view sothat the portion of the field of view is in-line with the opposing edges2330 a or 2330 b. An image of the weigh platter 110 and the counter 160(or the areas of interest 2320 a and 2320 b) may then be capturedwithout an item overlapping the edges 2330 a and 2330 b and stored as areference image.

At step 2505, an image of at least a portion of the weigh platter iscaptured (e.g., in response to a weigh request from the host 292). Forexample, the captured image may include the entire surface of the weighplatter 110 along with a portion of what surrounds weigh platter 110,such as the counter 160. However, instead of capturing an image of theentire surface of the weigh platter 110, the method 2500 may capture animage of the opposing edges 2330 a and 2330 b along with a portion ofwhat is located on each side of the opposing edges 2330 a and 2330 b(e.g., the areas of interest 2320 a and 2320 b). The captured image mayalso include other edges and surroundings thereof, such as a fruit railedge of the weigh platter 110.

At step 2510, one or more portions of the captured image correspondingone or more edges of the weigh platter are isolated. For example, theprocessor 2310 may read or assemble samples or pixels from the imager2300 corresponding to the areas of interest 2320 a and 2320 b (e.g.,read and store pixels from only certain columns and rows of the imager2300). The one or more portions of the image may be isolated in otherways, such as storing the entire image in a memory (e.g., memories 250or 260) and masking off certain portions of the image (e.g., processonly certain portions of the image). While the one or more portions ofthe image need not be isolated in every embodiment, processing a selectportion of the image may speed up the comparison to the reference image.

At step 2515, the captured image (or a portion thereof) is compared tothe reference image (or a corresponding portion thereof). Based on thecomparison, it can be determined whether an item extends between theweigh platter and another surface at step 2520. For example, theprocessor 2310 may take the sum of absolute differences between thepixels in the captured image and the reference image. In other words,the processor 2310 may take the absolute value of the difference betweeneach pixel in the captured image (or portion thereof) and acorresponding pixel in the reference image (e.g., by snaking through thecaptured image in a serpentine like manner), and summing the differencesto derive a metric of similarity between the images. If the images areidentical, the sum of absolute differences will be zero. However, if theimages are different (e.g., due to an item overlying an edge of theweigh platter), the sum of absolute differences will reflect thedifferences between the images. Thus, the processor 2310 may determinethat an item extends between the weigh platter and another surface ifthe sum of absolute differences calculation exceeds a certain thresholdwithin operational tolerances.

While, sum of absolute differences calculations may be used to comparethe captured image to the reference image, other methods may be used.For example, a sum of squared differences may be used. Additionally,other two-dimensional image processing techniques may be used, such asbackground subtraction and contrast enhancement. Further, the method2500 may search for one or more edges (e.g., edges 2330 a and 2330 b) inthe reference image using any number of edge detection techniques. Afteridentifying an edge in the reference image, the method 2500 may searchfor the same edge (in the same approximate relative location) in thecaptured image to determine if the edge is fully in view or at leastpartially blocked.

The reference image may be captured at any time and according to anytechnique. For example, the reference image may be captured and storedafter the imager 2300 has been installed (e.g., as part of a calibrationprocedure). In addition or alternatively, the reference image may beobtained in other manners, such as capturing the reference image whenthe scale indicates a weight of approximately zero (and it can thus beinferred that there are no items on the scale or partially on thescale). By way of another example, the reference image may be the otheropposing edge of the weigh platter (e.g., assuming the item does notoverlap the opposing edges in exactly the same manner, the auxiliaryscanner views 2410 a and 2410 b may be compared). Additionally, one ormore images of the weigh platter 110 and the counter 160 (or the areasof interest 2320 a and 2320 b) may be captured over time (e.g., daily,weekly, or monthly) to adjust or compensate for changes to or wear ofthe weigh platter over time (e.g., as part of a calibration routine runas the scanner initiates).

Upon determining that an item extends between the weigh platter andanother surface, the operator may be notified via the alert module 220(FIG. 2) that an item may not be accurately weighed (i.e., an itemextends between the weigh platter 110 and another surface, such as thecounter or frame of the scanner). Additionally or alternatively, themethod 2500 may halt the weighing operation until the item is properlypositioned via the interlock module 230.

One possible advantage of the edge vision scale guard is that existingscanner-scale systems may readily be upgraded in the field by providingthe user with the scale guard module 210 (e.g., stored on amachine-readable medium) comprising a set of instructions for capturingan image of the weigh platter (or a portion thereof) to a referenceimage, and one or more imagers (if required). Once the scale guardmodule 210 and any required imager(s) have been installed, the scannerwill be able to monitor the edges of the weigh platter to determinewhether an item might not be properly weighed. Part of the installationprocess may include identifying a particular make and model of scanner,so that the scale guard module can access a data table includingapproximate locations of the edges of the weigh platter within theimager's field of view.

The methods and systems disclosed herein may be implemented in or by anysuitable hardware, software, firmware, or combination thereof.Accordingly, as used herein a component or module can comprise hardware,software, firmware, or any combination thereof (e.g., self-containedhardware or software components that interact with a larger system). Forexample, the methods and systems may exist as one or more software orfirmware programs comprised of program instructions in source code,object code, executable code or other formats. A software module orcomponent may include any type of computer instruction or computerexecutable code located within a memory device or transmitted aselectronic signals over a system bus or wired or wireless network. Asoftware module or component may, for instance, comprise one or morephysical or logical blocks of computer instructions, which may beorganized as a routine, program, object, component, data structure,etc., that performs one or more tasks or implements particular abstractdata types.

In certain embodiments, a particular software module or component maycomprise disparate instructions stored in different locations of amemory device, which together implement the described functionality ofthe module. Indeed, a module may comprise a single instruction or manyinstructions, and may be distributed over several different codesegments, among different programs, and across several memory devices.Some embodiments may be practiced in a distributed computing environmentwhere tasks are performed by a remote processing device linked through acommunications network. In a distributed computing environment, softwaremodules may be located in local or remote memory storage devices. Inaddition, data being tied or rendered together in a database record maybe resident in the same memory device, or across several memory devices,and may be linked together in fields of a record in a database across anetwork.

Embodiments may include various steps, which may be embodied inmachine-executable instructions to be executed by a general-purposeprocessor, special-purpose processor, or other electronic device.Alternatively, the steps may be performed by hardware components thatinclude specific logic for performing the steps or by a combination ofhardware, software, firmware, or any combination thereof. A result oroutput from any step, such as a confirmation that the step has or hasnot been completed or an output value from the step, may be stored,displayed, printed, or transmitted over a wired or wireless network.

Embodiments may also be provided as a computer program product embodiedon a machine-readable storage medium having stored thereon instructions(in compressed or uncompressed form) that may be used to program acomputer (or other electronic device) to perform processes or methodsdescribed herein. The machine-readable storage medium may include, butis not limited to, hard drives, floppy diskettes, optical disks,CD-ROMs, DVDs, read-only memories (ROMs), random access memories (RAMs),EPROMs, EEPROMs, flash memory, magnetic or optical cards, solid-statememory devices, or other types of media/machine-readable medium suitablefor storing electronic instructions. Further, embodiments may also beprovided as a computer program product embodied on a machine-readablesignal (in compressed or uncompressed form). Examples ofmachine-readable signals, whether modulated using a carrier or not,include, but are not limited to, signals that a computer system ormachine hosting or running a computer program can be configured toaccess, including signals downloaded through the Internet or othernetworks. For example, distribution of software may be via CD-ROM or viaInternet download.

While embodiments disclosed herein have been discussed in combinationwith barcodes, the embodiments disclosed herein may be utilized by otherautomated data collection/capture techniques including, but not limitedto, magnetic stripes, optical card readers, voice recognition, and smartcard or radio frequency identification. Further, while the various scaleguard module embodiments described herein have been described withreference to a data reader or scanner system, the scale guard moduleembodiments described herein are equally applicable to other systemsthat incorporate or interact with a weigh scale, such as package orparcel handling machines and equipment and luggage sorting and handlingmachines and equipment. Additionally, while various examples of thescale guard module 210 have been described herein, other systems andmethods may be used to determine whether an item extends between theweigh platter 110 and the counter 160, which may affect the accuracy ofthe weight measurement. For example, the scale guard module 210 maycomprise any combination of the embodiments described herein or in U.S.Provisional Application No. 61/267,376, filed Dec. 7, 2009. Utilizingmultiple systems and methods to determine whether an item extendsbetween the weigh platter 110 and the counter 160 may add redundancy incase one or more of the systems fail (or produces an inaccurate result)and may produce a more accurate determination of whether an item extendsbetween the weigh platter 110 and the counter 160. Additionally,individual determinations of whether an item extends between the weighplatter and another surface from multiple systems and methods may beweighted to determine an overall confidence level of whether or not anitem extends between the weigh platter and another surface.

As should be appreciated in view of the teachings herein, certainembodiments may be capable of achieving certain advantages, including byway of example and not limitation one or more of the following: (1)providing a system and method for reducing scale shrinkage; (2) providenoninvasive system and method to reduce scale shrinkage; (3) providing asystem and method for reducing scale shrinkage with no additionalelectrical connections proximate the weigh platter; (4) providing a lowcost system for reducing scale shrinkage; (5) providing a system forreducing scale shrinkage utilizing existing components; (6) providing asystem for reducing scale shrinkage with minimal additional hardware;(7) providing a non-light-beam-based system for reducing scaleshrinkage; and (8) providing a system and method for reducing scaleshrinkage having no physical bump or barrier in a slide path of thescanner.

The terms and descriptions used herein are set forth by way ofillustration only and are not meant as limitations. Those skilled in theart will recognize that many variations can be made to the details ofthe above-described embodiments without departing from the underlyingprinciples of the invention. The scope of the invention should thereforebe determined only by the following claims (and their equivalents) inwhich all terms are to be understood in their broadest reasonable senseunless otherwise indicated.

1. A system for reducing weighing errors of an item being weighed on aweigh platter of a scale associated with a data reader installed in acheckout counter surface or other fixed object, the system comprising: aweigh platter including a top surface adjacent the checkout countersurface or other fixed object, the top surface of the weigh platterincluding a lateral edge that is adjacent an edge of the checkoutcounter surface or other fixed object; a data reader configured todetect a change in light reflected from a region proximate the lateraledge of the top surface of the weigh platter; and a controller coupledto the data reader, the controller configured to determine whether anitem rests partially on the checkout counter or other fixed object andpartially on the weigh platter based on whether the item blocks aportion of the light that would otherwise reflect off of said regionproximate the lateral edge.
 2. The system of claim 1, furthercomprising: a reference pattern positioned on a surface proximate andalong the lateral edge, wherein the data reader is configured to detectthe pattern when the pattern is unobstructed by an item and thecontroller is configured to determine whether an item blocks a portionof the light that would otherwise reflect off of the region proximatethe lateral edge of the top surface of the weigh platter based onwhether the item interrupts the reference pattern.
 3. The system ofclaim 2, wherein the data reader comprises an imaging based scanningsystem including an image sensor that detects an image of a targetwithin a field of view of the image sensor, and the imaging basedscanning system is configured such that a full extent of the referencepattern is within the field of view of the image sensor when thereference pattern is unobstructed.
 4. The system of claim 2, wherein thedata reader comprises a laser based scanning system configured togenerate a scan pattern along a scan arc, project the scan pattern ontoan optical code, and detect light reflected by the optical code fordecoding the optical code, and the laser based scanning system isfurther configured to project at least a portion of the scan arc along afull extent of the pattern when the pattern is unobstructed and todetect light reflected by the pattern.
 5. The system of claim 1, furthercomprising: an imager configured to capture an image of the regionproximate the lateral edge of the top surface of the weigh platter; anda memory for storing a reference image, the reference image comprisingan image of the region proximate the lateral edge of the top surface ofthe weigh platter when an item does not rest partially on the weighplatter and partially on the checkout counter or other fixed object,wherein the controller is configured to cause the imager to capture animage of the region proximate the lateral edge of the top surface of theweigh platter and determine whether an item blocks a portion of thelight that would otherwise reflect off of the region of the top surfaceof the weigh platter based on a comparison of the captured image and thereference image.
 6. A system for reducing weighing errors of an itembeing weighed on a weigh platter of a scanner-scale associated with adata reader installed in a checkout counter surface or other fixedobject, the system comprising: a weigh platter including a top surfaceadjacent the checkout counter surface or other fixed object, the topsurface of the weigh platter including first and second lateral edgesthat are adjacent respective first and second edges of the checkoutcounter surface or other fixed object; a first reference patternpositioned on a surface proximate and along the first lateral edge ofthe weigh platter; a data reader configured to detect the first patternwhen the first pattern is unobstructed; and a controller coupled to thedata reader, the controller configured to determine whether an itemrests partially off the weigh platter based on whether the iteminterrupts the first pattern.
 7. The system of claim 6, furthercomprising: a second reference pattern positioned on a surface proximateand along the second lateral edge of the weigh platter, wherein the datareader is configured to detect the second pattern when the secondpattern is unobstructed and the controller is configured to determinewhether an item rests partially off the weigh platter based on whetherthe item interrupts at least one of the first pattern and the secondpattern.
 8. The system of claim 6, wherein the data reader comprises animaging based scanning system including an image sensor that detects animage of a target within a field of view of the image sensor, and theimaging based scanning system is configured such that a full extent ofthe first pattern is within the field of view of the image sensor whenthe first pattern is unobstructed.
 9. The system of claim 6, wherein thedata reader comprises a laser based scanning system configured togenerate a scan pattern along a scan arc, project the scan pattern ontoan optical code, and detect light reflected by the optical code fordecoding the optical code, and the laser based scanning system isfurther configured to project at least a portion of the scan arc along afull extent of the first pattern when the first pattern is unobstructedand to detect light reflected by the first pattern.
 10. The system ofclaim 6, further comprising: a set of mirrors configured to redirect aline-of-sight of the data reader to read along a lengthwise region ofthe surface proximate and along the first lateral edge of the weighplatter corresponding to the first reference pattern.
 11. The system ofclaim 6, further comprising: a filter coupled to the data reader,wherein the filter is tuned to a frequency of the first pattern, anoutput of the filter indicating whether the item at least partiallyinterrupts the first pattern, and wherein the controller is configuredto monitor the output of the filter to determine whether the item restspartially off the weigh platter.
 12. The system of claim 6, furthercomprising: an edge detector coupled to the data reader, wherein theedge detector is configured to detect edge transitions in the firstpattern and the controller is configured to monitor the number of edgetransitions detected by the edge detector to determine whether the itemrests partially off the weigh platter.
 13. The system of claim 6,further comprising: an interlock component coupled to the controller andconfigured to disable a weigh function associated with the weigh platterwhen the controller determines that an item rests partially off theweigh platter.
 14. The system of claim 6, further comprising: externalindicia configured to notify an operator of whether an item restspartially off the weigh platter.
 15. The system of claim 6 wherein thefirst pattern comprises regularly spaced apart features.
 16. The systemof claim 6 wherein the first pattern comprises non-uniformly spacedapart features and the spacing between the features is selected tocompensate for a scan angle of the data reader so that a frequency ofthe first pattern is approximately constant when the data reader detectsthe first pattern when the first pattern is unobstructed.
 17. The systemof claim 6 wherein the first pattern comprises a series of holesextending through the top surface of the weigh platter to thereby createan alternating pattern of high and low reflectance sections on the topsurface of the weigh platter.
 18. The system of claim 6 wherein thefirst pattern comprises a series of stamped depressions, whereby thestamped depressions create an alternating pattern of high and lowreflectance sections on the top surface of the weigh platter.
 19. Thesystem of claim 6 wherein the first pattern comprises a plurality ofspaced apart retroreflective sections to thereby create an alternatingpattern of high and low reflectance sections on the top surface of theweigh platter.
 20. The system of claim 6 wherein the top surface of theweigh platter is brushed in a direction substantially parallel to a scandirection of the item to thereby create a high reflectance surface thatis resistant to wear.
 21. A method for reducing weighing errors of anitem being weighed on a weigh platter associated with a data reader,said weigh platter including a top surface having first and secondlateral edges that are adjacent a checkout counter or other fixedobject, the method comprising the steps of: scanning, via the datareader, a first reference pattern positioned proximate and along a firstlateral edge of the top surface of the weigh platter; determiningwhether a full extent of the first pattern is detected by the datareader; and determining whether an item rests partially off the weighplatter based on whether the data reader detected the full extent of thefirst reference pattern.
 22. The method of claim 21, wherein the datareader comprises an imaging based scanning system and wherein the stepof scanning the first reference pattern comprises capturing an imagecorresponding to a location of the first reference pattern and analyzingthe captured image to determine whether a number of edge transitions inthe captured image corresponds to a number of edge transitions in thefull extent of the first reference pattern.
 23. The method of claim 21,wherein the data reader comprises a laser based scanning system andwherein the step of scanning the first reference pattern comprisesprojecting a scan line along the full extent of the first referencepattern and monitoring light reflected by the first reference patternfor a frequency of the first pattern over the scan line.
 24. The methodof claim 21, further comprising: upon determining that an item restspartially off the weigh platter, notifying an operator that an itemrests partially off the weigh platter.
 25. A system for reducingweighing errors of an item being weighed on a weigh platter associatedwith a data reader disposed in a checkout counter of other station, thesystem comprising: a weigh platter including a top surface with firstand second lateral edges; an imager configured to capture an image of aportion of the top surface of the weigh platter, including regionsproximate and along the first and second lateral edges of the topsurface of the weigh platter; a memory for storing a reference image,the reference image comprising an image of the portion of the topsurface of the weigh platter when an item does not rest partially offthe weigh platter; and a processor coupled to the imager and the memory,the processor configured to cause the imager to capture an image of theportion of the top surface of the weigh platter and determine whether anitem rests partially off the weigh platter based on a comparison of thecaptured image and the reference image.
 26. The system of claim 25,wherein the data reader comprises an imaging based scanning systemincluding an image sensor and the imager comprises the image sensor ofthe imaging based scanning system.
 27. The system of claim 25, whereinthe processor is configured to calculate a sum-of-absolute-differencesbetween corresponding pairs of captured image pixels and reference imagepixels to determine whether an item rests partially off the weighplatter.
 28. The system of claim 25, further comprising: externalindicia configured to notify an operator of whether an item restspartially off the weigh platter.
 29. A method for reducing weighingerrors of an item being weighed on a weigh platter associated with adata reader, said weigh platter including a top surface having first andsecond lateral edges that are adjacent a checkout counter or other fixedobject, the method comprising the steps of: capturing an image of aportion of the top surface of the weigh platter including regionsproximate and along the first edge of the top surface of the weighplatter; comparing the captured image with a reference image, thereference image comprising an image of a portion of the top surface ofthe weigh platter including regions proximate and along the adjacentfirst and second lateral edges of the top surfaces of the weigh platterwhen an item does not rest partially off the weigh platter; and based onthe comparing of the captured image and the reference image, determiningwhether an item rests partially off the weigh platter.
 30. The method ofclaim 29, wherein the image is captured in response to a requestreceived from a host.
 31. The method of claim 29, wherein the step ofcomparing the captured image with a reference image comprisescalculating a sum-of-absolute-differences between corresponding pairs ofcaptured image pixels and reference image pixels.
 32. The method ofclaim 29, further comprising: isolating a set of captured image pixelscorresponding to the first edge of the top surface of the weigh platter,wherein the isolated set of captured image pixels are compared tocorresponding reference image pixels.
 33. The method of claim 29,further comprising: periodically capturing an updated reference image,the updated reference image comprising an image of a portion of the topsurface of the weigh platter including regions proximate and along thefirst edge of the top surface of the weigh platter when an item does notrest partially off the weigh platter; and updating the reference imagewith the updated reference image.
 34. A system for reducing weighingerrors of an item being weighed on a weigh platter associated with adata reader, the system comprising: a weigh platter including a topsurface with a peripheral edge that is adjacent a checkout counter orother fixed object; a radiating antenna disposed proximate and to oneside of the peripheral edge of the weigh platter, the radiating antennaconfigured to transmit electromagnetic waves across the peripheral edgeof the weigh platter; a receiving antenna disposed on a side of theperipheral edge of the weigh platter opposite the radiating antenna, thereceiving antenna configured to receive the electromagnetic waves fromthe radiating antenna; a transmitter coupled to the radiating antenna,the transmitter configured to drive the radiating antenna with a signalso that the radiating antenna transmits the electromagnetic waves acrossthe peripheral edge of the weigh platter; and a receiver coupled to thereceiving antenna, the receiver configured to monitor the receivingantenna for an alteration in a coupling of the electromagnetic wavesfrom the radiating antenna to the receiving antenna to determine whetheran item rests partially off the weigh platter.
 35. The system of claim34, wherein the radiating antenna comprises the weigh platter.
 36. Thesystem of claim 34, wherein the receiving antenna comprises a loop ofwire at least partially surrounding the weigh platter.
 37. The system ofclaim 34, wherein the radiating antenna is configured to transmitelectromagnetic waves within the range of approximately three megahertzto approximately thirty megahertz and the receiving antenna isconfigured to receive electromagnetic waves within the range ofapproximately three megahertz to approximately thirty megahertz.
 38. Thesystem of claim 34, further comprising: a controller coupled to thereceiver, the controller configured to monitor an output of the receiverto determine whether an item rests partially off the weigh platter. 39.The system of claim 34, further comprising: external indicia configuredto notify an operator of whether an item rests partially off the weighplatter.
 40. A method for reducing weighing errors of an item beingweighed on a weigh platter associated with a data reader, the methodcomprising: transmitting across a peripheral edge of the weigh platterfrom a radiating antenna to a receiving antenna electromagnetic waves;monitoring the receiving antenna to detect an alteration in a couplingof the electromagnetic waves from the radiating antenna to the receivingantenna; and determining whether an item rests partially off the weighplatter based whether an alteration in the coupling of theelectromagnetic waves from the radiating antenna to the receivingantenna is detected.
 41. The method of claim 40, wherein the step ofmonitoring the receiving antenna to detect an alteration in a couplingof the electromagnetic waves from the radiating antenna to the receivingantenna comprises comparing an amplitude of the electromagnetic wavesreceived at the receiving antenna to a predetermined threshold.
 42. Themethod of claim 41, further comprising: periodically measuring anamplitude of the electromagnetic waves received at the receiving antennawhen an item does not rest partially off the weigh platter; and updatingthe predetermined threshold with the measured amplitude.
 43. The methodof claim 40, further comprising: configuring the weigh platter to form aradiating antenna.
 44. A system for reducing weighing errors of an itembeing weighed on a weigh platter associated with a data reader, thesystem comprising: a weigh platter including a top surface with firstand second opposing edges; a housing section including a lower housingsection supporting the weigh platter and an upper housing section risingabove a top surface of the weigh platter on a side of the weigh platterthat extends between the first and second opposing edges; a first set oftransducers disposed along the adjacent first and second edges of thetop surface, the first set of transducers configured to transmit orreceive non-electromagnetic compression waves; a second set oftransducers disposed on the upper housing section, the second set oftransducers configured to transmit or receive non-electromagneticcompression waves; a transmitter coupled to one of the first set oftransducers or the second set of transducers, the transmitter configuredto drive the set of transducers with a signal so that the set oftransducers transmit non-electromagnetic compression waves; and areceiver coupled to the other one of the first set of transducers or thesecond set of transducers, the receiver configured to monitor the set oftransducers coupled to the receiver for an alteration in amplitude ofincident compression waves transmitted by the set of transducers drivenby the transmitter to determine whether an item rests partially off theweigh platter.
 45. The system of claim 44, wherein the first set oftransducers comprise a plurality of individual linearly-alignedtransducers configured to transmit non-electromagnetic compressionwaves, the transmitter is coupled to the first set of transducers, thesecond set of transducers comprise a single transducer configured toreceive the compression waves transmitted by the first set oftransducers, and the receiver is coupled to the second set oftransducers.
 46. The system of claim 44, wherein the second set oftransducers comprise a single transducer configured to transmitnon-electromagnetic compression waves, the transmitter is coupled to thesecond set of transducers, the first set of transducers comprise aplurality of individual linearly-aligned transducers configured toreceive the compression waves transmitted by the first set oftransducers, and the receiver is coupled to the first set oftransducers.
 47. The system of claim 44, wherein the first and secondsets of transducers comprise a piezoelectric film.
 48. The system ofclaim 44, wherein the first and second sets of transducers areconfigured to transmit or receive non-electromagnetic compression waveswithin the range of approximately 200 kilohertz to approximately 400kilohertz.
 49. The system of claim 44, further comprising: a controllercoupled to the receiver, the controller configured to monitor an outputof the receiver to determine whether an item rests partially off theweigh platter.
 50. The system of claim 44, further comprising: externalindicia configured to notify an operator whether an item rests partiallyon the weigh platter and partially on the checkout counter or otherfixed object.
 51. A method for reducing weighing errors of an item beingweighed on a weigh platter associated with a data reader, said datareader including an upper housing section rising above a top surface ofthe weigh platter, a first set of transducers positioned along at leasta portion of a peripheral edge of the weigh platter, and a second set oftransducers disposed on the upper housing section, said first and secondsets of transducers configured to transmit or receivenon-electromagnetic compression waves, the method comprising:transmitting from a set of emitters to a set of sensorsnon-electromagnetic compression waves, the set of emitters comprisingone of the first set of transducers or the second set of transducers andthe set of sensors comprising the other one of the first set oftransducers or the second set of transducers; monitoring the set ofsensors to detect an alteration in amplitude of incident compressionwaves transmitted by the set of emitters; and determining whether anitem rests partially off the weigh platter based whether an alterationin the amplitude of incident compression waves transmitted by the set ofemitters is detected at the set of sensors.
 52. The method of claim 51,wherein the set of emitters comprise the second set of transducers andthe set of sensors comprise the first set of transducers.
 53. The methodof claim 51, wherein the first set of transducers comprise a pluralityof individual linearly-aligned transducers and the second set oftransducers comprise a single transducer.
 54. The method of claim 51,wherein the step of monitoring the set of sensors to detect analteration in amplitude of incident compression waves transmitted by theset of emitters comprises comparing an amplitude of the incidentcompression waves received by the set of sensors to a predeterminedthreshold.
 55. The method of claim 54, further comprising: periodicallymeasuring an amplitude of the compression waves received by the set ofsensors when an item does not rest partially off the weigh platter; andupdating the predetermined threshold with the measured amplitude.
 56. Asystem for reducing weighing errors of an item being weighed on a weighplatter associated with a data reader installed in a checkout counter ofother fixed object, the system comprising: a weigh platter including atop surface with first and second opposing edges that are adjacent thecheckout counter or other fixed object; a first set of transducersdisposed along the adjacent first edges of the top surface, the firstset of transducers configured to transmit and receivenon-electromagnetic compression waves; a second set of transducersdisposed along the adjacent second edges of the top surface, the secondset of transducers configured to transmit and receivenon-electromagnetic compression waves; a transmitter coupled to thefirst and second sets of transducers, the transmitter configured todrive the transducers with a signal so that the transducers transmitnon-electromagnetic compression waves away from the top surface of theweigh platter; and a receiver coupled to the first and second sets oftransducers, the receiver configured to monitor the transducers todetect compression waves reflected by an item toward the top surface ofthe weigh platter to determine whether an item rests partially off theweigh platter.